help-docs: Move help center documentation to top level directory.

These files are not Jinja2 templates, so there's no reason that they needed
to be inside `templates/zerver`. Moving them to the top level reflects their
importance and also makes it feel nicer to work on editing the help center content, 
without it being unnecessary buried deep in the codebase.

help/manage-your-uploaded-files.md

@@ -0,0 +1,65 @@
+# Manage your uploaded files
+
+Zulip lets you view, sort, filter, download, and delete any files that you have
+uploaded.
+
+## View a file
+
+{start_tabs}
+
+{settings_tab|uploaded-files}
+
+1. Click on the name of a file in the **File** column.
+
+!!! tip ""
+
+    You can also view a file in the context of the conversations where it
+    was mentioned by clicking on a message ID in the **Mentioned in** column.
+
+{end_tabs}
+
+## Sort your files
+
+You can sort your uploaded files by name, upload date, message ID, and size.
+
+{start_tabs}
+
+{settings_tab|uploaded-files}
+
+1. Click on the name of a column to toggle between ascending and descending order.
+
+!!! tip ""
+
+    You can filter your current view by using the **search box** near the top
+    right corner of the menu.
+
+{end_tabs}
+
+## Download a file
+{start_tabs}
+
+{settings_tab|uploaded-files}
+
+1. In the **Actions** column, click the **download file**
+   (<i class="fa fa-download"></i>) icon for the file you want to download.
+
+{end_tabs}
+
+## Delete a file
+
+{start_tabs}
+
+{settings_tab|uploaded-files}
+
+1. In the **Actions** column, click the **delete file**
+   (<i class="fa fa-trash-o"></i>) icon for the file you want to remove.
+
+1. Approve by clicking **Delete**. If you delete a file, your message will still
+   contain a file link, but the link will no longer work.
+
+{end_tabs}
+
+## Related articles
+
+* [Share and upload files](/help/share-and-upload-files)
+* [View and browse images](/help/view-and-browse-images)