[[ Bug 13762 ]] Make contains respect grapheme boundaries.
[[ Foundation ]] Ensure MapGraphemeIndicies uses MapCodepointIndicies.
[[ Bug 13762 ]] Changed begins with / ends with to ensure it works with grapheme boundaries.
[[ Bug 13762 ]] Factored out grapheme boundary check.
[[ Bug 13762 ]] Update the mark point when fetching codepoints from the state
Merge pull request #1332 from runrevali/bugfix-13762

Bugfix 13762