RTE link autocomplete should support headings within pages as well as pages

When entering a link using [ notation, the Rich Text Editor should be smart enough to "scan ahead" for headings and/or anchors in the target page, and allow direct linking to headings instead of the insanely convoluted syntax we have to use now.

This is basic functionality, and the lack of ability to link directly to headings is actually impeding adoption at our company.