Themes: Add more help and documentation when editing theme files

[karmatosed]

Add:

“Looks like you’re trying to edit your theme! We recommend creating a [child theme](link)" instead.

This will let you make changes to your theme without accidentally breaking anything.” Except with better copy. Maybe also a “make child theme” one-click button that generates a child theme with a functions.php and style.css.

[swissspidy]

Can we handle the warning thing in #41075 and keep this one for the help part only? I think there are some plugins that let you create child themes that we could look at.

[melchoyce]

Moving the warning stuff over to #31779. Let's keep this for other ideas and enhancements around editing theme files for now.

[melchoyce]

Some ideas...

• Could we add autocomplete for add_theme_support() if you're in functions.php?
• Could we add autocomplete for things like get_template_part() or get_[header, footer, etc.]() in template files?
• Could we provide any helpful hints or not-quite-inline documentation?