Support clicking <a> tags and highlighting text.

[Bravotic]

When text is added to a row, lets keep track of its position its added at and keep a list of text at positions, stored in plain text. When a position known to have text is selected, we can simply refer to the list of text at positions. Likewise, we can keep track of where links are using this.

[Bravotic]

This would probably need to be added into the mothman.c function addRowToPage, where we could update where exactly the row is starting, otherwise we would need to disable centered text. Text that is aligned to the center causes incorrect x/y positions since that is done in Drawlib and not in mothman.c

[Bravotic]

This could actually be done by keeping a bitmap of the text, and simply overlaying it on a selected background when the text is selected. This would select it by entire word (which Mothra does) and should be somewhat efficient.