run-mailcap: conform with style guide

[Managor]

• The page(s) are in the correct platform directories: common, linux, osx, windows, sunos, android, etc.
• The page(s) have at most 8 examples.
• The page description(s) have links to documentation or a homepage.
• The page(s) follow the content guidelines.
• The page(s) follow the style guide.
• The PR title conforms to the recommended templates.
• Version of the command being documented (if known):

[Managor]

This part of the page was last touched 10 years ago

[spageektti]

Could you also update example descriptions? Some of them aren't imperative.

[Managor]

That should be better