Dashicons page should have a usage example for associating with content types

[DrewAPicture]

It's great that Mel's Dashicons page was ​integrated with DevHub, though I feel like it's missing example usage for associating dashicons with content types in the dashboard. This would be in addition to the existing CSS usage section.

I believe we have that information elsewhere, maybe in one of the handbooks, but it would be especially pertinent in this context on that page.

[ryelle]

Here's a first pass on adding "WordPress Usage", with add_menu_page and register_post_type examples grabbed from the plugin handbook (though neither actually had a dashicons example, with ​add_menu_page using a .png icon, and no icon in ​register_post_type).

CSS Usage became CSS/HTML Usage, since we probably want to encourage using the core helper classes, and has 2 examples for the 2 classes.

I also reordered the instructions: adding WordPress Usage first, then CSS/HTML Usage, and moving Photoshop Usage to the end.

[DrewAPicture]

Interesting. I kind of wonder if maybe we should just put it in the Plugin Developer handbook and link over to it instead of duplicating the effort. Food for thought.

[coffee2code]

In 1271:

developer.wordpress.org: Add usage examples for add_menu_page() and register_post_type() on dashicons page.

Fixes #758.
Props ryelle.