Add stylelint to repository

.stylelintrc

@@ -0,0 +1,59 @@
+{
+  "rules": {
+    "color-hex-case": "lower",
+    "color-no-invalid-hex": true,
+
+    "function-calc-no-unspaced-operator": true,
+    "function-comma-space-after": "always-single-line",
+    "function-comma-space-before": "never",
+    "function-name-case": "lower",
+    "function-url-quotes": "always",
+    "function-whitespace-after": "always",
+
+    "number-leading-zero": "always",
+    "number-no-trailing-zeros": true,
+    "length-zero-no-unit": true,
+
+    "string-no-newline": true,
+    "string-quotes": "single",
+
+    "unit-case": "lower",
+    "unit-no-unknown": true,
+    "unit-whitelist": ["px", "%", "deg", "ms", "em", "vh", "vw", "rem"],
+
+    "value-list-comma-space-after": "always-single-line",
+    "value-list-comma-space-before": "never",
+
+    "shorthand-property-no-redundant-values": true,
+
+    "property-case": "lower",
+
+    "declaration-block-no-duplicate-properties": true,
+    "declaration-block-no-ignored-properties": true,
+    "declaration-block-trailing-semicolon": "always",
+    "declaration-block-single-line-max-declarations": 0,
+    "declaration-block-semicolon-space-before": "never",
+    "declaration-block-semicolon-space-after": "always-single-line",
+    "declaration-block-semicolon-newline-before": "never-multi-line",
+    "declaration-block-semicolon-newline-after": "always-multi-line",
+
+    "block-closing-brace-newline-after": "always",
+    "block-closing-brace-newline-before": "always-multi-line",
+    "block-no-empty": true,
+    "block-opening-brace-newline-after": "always-multi-line",
+    "block-opening-brace-space-before": "always",
+
+    "selector-attribute-brackets-space-inside": "never",
+    "selector-attribute-operator-space-after": "never",
+    "selector-attribute-operator-space-before": "never",
+    "selector-combinator-space-after": "always",
+    "selector-combinator-space-before": "always",
+    "selector-pseudo-class-case": "lower",
+    "selector-pseudo-class-parentheses-space-inside": "always",
+    "selector-pseudo-element-case": "lower",
+    "selector-pseudo-element-colon-notation": "double",
+    "selector-pseudo-element-no-unknown": true,
+    "selector-type-case": "lower",
+    "selector-no-id": true
+  }
+}

Gruntfile.js

@@ -28,6 +28,16 @@ module.exports = function( grunt ) {
 			]
 		},
 
+		// Sass linting with Stylelint.
+		stylelint: {
+			options: {
+				stylelintrc: '.stylelintrc'
+			},
+			all: [
+				'<%= dirs.css %>/*.scss',
+			]
+		},
+
 		// Minify .js files.
 		uglify: {
 			options: {
@@ -228,6 +238,7 @@ module.exports = function( grunt ) {
 	grunt.loadNpmTasks( 'grunt-contrib-cssmin' );
 	grunt.loadNpmTasks( 'grunt-contrib-watch' );
 	grunt.loadNpmTasks( 'grunt-contrib-clean' );
+	grunt.loadNpmTasks( 'grunt-stylelint' );
 
 	// Register tasks
 	grunt.registerTask( 'default', [

package.json

@@ -19,6 +19,7 @@
     "grunt-contrib-uglify": "~1.0.0",
     "grunt-contrib-watch": "~1.0.0",
     "grunt-shell": "~1.3.0",
+    "grunt-stylelint": "^0.6.0",
     "grunt-wp-i18n": "~0.5.4",
     "node-bourbon": "~4.2.3"
   },