Description

Fixes marked text input for sequences longer than one marked character. Also ensures marked text works consistently with multiple cursors and adds testing for the marked text functionality.

Also:

• Fixes a few lint markers in test files that have caused issues for others.
• Adds a publicTextView.markedTextAttributes property for modifying the marked text attributes if desired.

Related Issues

• closes🐞 When typing Chinese, sometimes pressing a key will get several more letters #37
• closes🐞 Typing with Dictation results in duplicate characters #36
• closes🐞 Input not cleared when using Chinese input method #26
• closes🐞 Compile errors by SwiftLintPlugin CodeEditSourceEditor#188

Checklist

• I read and understood thecontributing guide as well as thecode of conduct
• The issues this PR addresses are related to each other
• My changes generate no new warnings
• My code builds and runs on my machine
• My changes are all related to the related issue above
• I documented my code

Screenshots