documentation: Update tutorial for writing help center documentation.

Updates the tutorial for writing help center articles to encourage
contributors to add to or enhance the existing help center docs
before writing a new articles for new features.

Also, generally updates references to 'user documentation' to be
'help center documentation'.

Additionally, updates some headers within the tutorials for clarity
and consistency, and adds some linkifying throughout the section on
writing documentation.

docs/translating/german.md

@@ -226,13 +226,13 @@ and there is no German equivalent, talking of "Views" is preferable in the
 developer documentation and makes it easier to rely on parts of the German
 _and_ parts of the English documentation.
 
-- View - **Ansicht** (User documentation)
+- View - **Ansicht** (User-facing documentation)
 
-For the user documentation, we want to use "Ansicht" instead of "view", as
-"Ansicht" provides a translated description for what you think of when hearing
-"view". "Ansicht" is not desirable for the developer documentation, since it
-does not emphasize the developing aspects of views (in contrast to anglicisms,
-which Germans often link to IT-related definitions).
+For user-facing documentation, we want to use "Ansicht" instead of "view",
+as "Ansicht" provides a translated description for what you think of when
+hearing "view". "Ansicht" is not desirable for the developer documentation,
+since it does not emphasize the developing aspects of views (in contrast to
+anglicisms, which Germans often link to IT-related definitions).
 
 _"Ansicht" (Transifex)_