Fix list alignment

Resolve #420

- Remove `margin-top` for the first child in various list items, to improve alignment.
- Add examples of lists to `docs/tests/styling`.

_sass/content.scss

@@ -154,6 +154,41 @@
       visibility: hidden;
     }
   }
+  
+  dd {
+    blockquote,
+    div,
+    dl,
+    dt,
+    h1,
+    h2,
+    h3,
+    h4,
+    h5,
+    h6,
+    li,
+    ol,
+    p,
+    pre,
+    table,
+    ul,
+    .table-wrapper {
+      &:first-child {
+        margin-top: 0;
+      }
+    }
+  }
+
+  dd, 
+  ol, 
+  ul {
+    dl:first-child {
+      dt:first-child,
+      dd:nth-child(2) {
+        margin-top: 0;
+      }
+    }
+  }
 
   .anchor-heading:hover,
   h1:hover > .anchor-heading,

docs/tests/styling/dl.md

@@ -0,0 +1,83 @@
+---
+layout: default
+title: Description lists
+parent: Styling
+grand_parent: Tests
+---
+
+# Description lists
+
+The first child element of each `dd` element in a `dl` list should be aligned with the preceding `dt` element in the following examples.
+
+term
+
+: paragraph text
+
+  paragraph text
+
+term
+
+: ### Header
+
+  paragraph text
+
+term
+
+: > block quote
+
+  paragraph text
+
+term
+
+: ```sh
+  fenced code block
+  ```
+
+  paragraph text
+
+term
+
+: + unordered list item
+  + unordered list item
+
+  paragraph text
+
+term
+
+: 1. ordered list item
+  2. ordered list item
+
+  paragraph text
+
+term
+
+: sub-term
+  : sub-description
+  
+  sub-term
+  : sub-description
+
+  paragraph text
+
+term
+
+: |-----------------+------------+-----------------+----------------|
+  | Default aligned |Left aligned| Center aligned  | Right aligned  |
+  |-----------------|:-----------|:---------------:|---------------:|
+  | First body part |Second cell | Third cell      | fourth cell    |
+  | Second line     |foo         | **strong**      | baz            |
+  | Third line      |quux        | baz             | bar            |
+  |-----------------+------------+-----------------+----------------|
+  | Second body     |            |                 |                |
+  | 2 line          |            |                 |                |
+  |=================+============+=================+================|
+  | Footer row      |            |                 |                |
+  |-----------------+------------+-----------------+----------------|
+
+  paragraph text
+
+term
+
+: ***
+
+  paragraph text

docs/tests/styling/index.md

@@ -0,0 +1,8 @@
+---
+layout: default
+title: Styling
+parent: Tests
+has_children: true
+---
+
+# Styling

docs/tests/styling/ol.md

@@ -0,0 +1,65 @@
+---
+layout: default
+title: Ordered lists
+parent: Styling
+grand_parent: Tests
+---
+
+# Ordered lists
+
+The first child element of each `li` element in an `ol` list should be aligned with the preceding label in the following examples.
+
+1.  paragraph text
+
+    paragraph text
+
+1.  ### Header
+
+    paragraph text
+
+1.  > block quote
+
+    paragraph text
+
+1.  ```sh
+    fenced code block
+    ```
+
+    paragraph text
+
+1.  + unordered list item
+    + unordered list item
+
+    paragraph text
+
+1.  1. ordered list item
+    2. ordered list item
+
+    paragraph text
+
+1.  term
+    : description
+  
+    term
+    : description
+
+    paragraph text
+
+1.  |-----------------+------------+-----------------+----------------|
+    | Default aligned |Left aligned| Center aligned  | Right aligned  |
+    |-----------------|:-----------|:---------------:|---------------:|
+    | First body part |Second cell | Third cell      | fourth cell    |
+    | Second line     |foo         | **strong**      | baz            |
+    | Third line      |quux        | baz             | bar            |
+    |-----------------+------------+-----------------+----------------|
+    | Second body     |            |                 |                |
+    | 2 line          |            |                 |                |
+    |=================+============+=================+================|
+    | Footer row      |            |                 |                |
+    |-----------------+------------+-----------------+----------------|
+
+    paragraph text
+
+1.  ***
+
+    paragraph text

docs/tests/styling/ul.md

@@ -0,0 +1,65 @@
+---
+layout: default
+title: Unordered lists
+parent: Styling
+grand_parent: Tests
+---
+
+# Unordered lists
+
+The first child element of each `li` element in a `ul` list should be aligned with the preceding bullet in the following examples.
+
+- paragraph text
+
+  paragraph text
+
+- ### Header
+
+  paragraph text
+
+- > block quote
+
+  paragraph text
+
+- ```sh
+  fenced code block
+  ```
+
+  paragraph text
+
+- + unordered list item
+  + unordered list item
+
+  paragraph text
+
+- 1. ordered list item
+  2. ordered list item
+
+  paragraph text
+
+- term
+  : description
+  
+  term
+  : description
+
+  paragraph text
+
+- |-----------------+------------+-----------------+----------------|
+  | Default aligned |Left aligned| Center aligned  | Right aligned  |
+  |-----------------|:-----------|:---------------:|---------------:|
+  | First body part |Second cell | Third cell      | fourth cell    |
+  | Second line     |foo         | **strong**      | baz            |
+  | Third line      |quux        | baz             | bar            |
+  |-----------------+------------+-----------------+----------------|
+  | Second body     |            |                 |                |
+  | 2 line          |            |                 |                |
+  |=================+============+=================+================|
+  | Footer row      |            |                 |                |
+  |-----------------+------------+-----------------+----------------|
+
+  paragraph text
+
+- ***
+
+  paragraph text