az-appconfig: add page

[Juwana-Zerman]

• The page (if new), does not already exist in the repository.
• The page is in the correct platform directory (common/, linux/, etc.)
• The page has 8 or fewer examples.
• The PR title conforms to the recommended templates.
• The page follows the content guidelines.
• The page description includes a link to documentation or a homepage (if applicable).

Version of the command being documented (if known):

For: #6141

[navarroaxel]

Sorry for the delay to review.

[sbrl]

Removed review-needed, as this is waiting on the OP.

[sbrl]

Thanks, @Juwana-Zerman!