Downloads: add docs (https://github.com/woocommerce/woocommerce-admin/pull/3807)

* Downloads: add docs

* better screenshot

* note about timestamps being UTC

* timestamp -> date

plugins/woocommerce-admin/docs/woocommerce.com/analytics-downloads-report.md

@@ -1 +1,27 @@
 # Downloads Report
+
+The Downloads Report provides insight into the performance of your store's downloadable products. Downloads counts are a total including multiple from the same IP address. Please note that dates are representantive of UTC time as opposed to local timezone as other reports are.
+
+### All Downloads View
+
+By default, the Downloads Report displays the unfiltered All Downloads View. Each download is represented in the table and chart.
+
+![Downloads Report All Downloads View](images/analytics-downloads-report.png)
+
+### Advanced Filters
+
+There are several filters available to the Downloads Report:
+
+- Product
+- Username
+- Order number
+- IP Address
+
+![Downloads Report Advanced Filters](images/analytics-downloads-report-advanced-filters.png)
+
+### Report Sorting
+
+The report table allows sorting by the following columns:
+
+- Date
+- Product Title