Support GDEF Ligature Caret List Table

[Lohann]

I noticed that the Ligature Caret List Table parsing is being skipped, I need this table in order to properly position the cursor and highlight text in a text editor when dealing with ligatures such as fi, ffi, etc.

• https://learn.microsoft.com/en-us/typography/opentype/spec/gdef#ligature-caret-list-table-overview

Also seems that apple have its own custom ligature Caret Table called lcar:

• https://developer.apple.com/fonts/TrueType-Reference-Manual/RM06/Chap6lcar.html

[RazrFalcon]

Yes, this feature isn't needed by harfbuzz/rustybuzz, therefore there were no need in implementing it.

[daprahamian]

Hiya! It looks like I need the GDEF ligature caret list table as well. Would you be receptive to a PR implementing this?

[RazrFalcon]

Sure, patches are welcome.