Improve Hints mode in various ways

Improve Hints mode in various ways

- After having filtered hint markers by at least one character, select
  the entire text for the highlighted markers' elements. This makes it
  way easier to notice that you can stop typing and press `<enter>`
  instead to activate your desired hint marker.

- Because of the above point, it is now less important to make the
  highlighted hint markers stand out very much compared to other
  markers. So the styling has been changed to a more modest
  highlighting.

- Fixed: Links with the same href weren't getting the same hint after
  filtering hint markers by element text.

- Improved: After having filtered hint markers by element text, sort the
  markers by element text length, rather than element area. A large
  element might have less text than a smaller element.

- Improved: Don't allow typing more non-hint chars when all remaining
  markers have the same hint. This means less backspacing for the user
  in case of typos.

- Fixed: After having filtered hint markers by element text until all
  remaining markers have the same hint, _any_ hint char would activate
  the hint markers, even if that one didn't match the hint.