Fix: Handle deleteText for more than Thai language

[seanghay]

Description

Currently, it deletes a grapheme cluster at a time for Khmer, Lao, and Burmese. Add the same functionality as Thai language.

https://en.wikipedia.org/wiki/Khmer_script

https://en.wikipedia.org/wiki/Lao_script

https://en.wikipedia.org/wiki/Burmese_alphabet

Checks

• The new code matches the existing patterns and styles.
• The tests pass with yarn test.
• The linter passes with yarn lint. (Fix errors with yarn fix.)
• The relevant examples still work. (Run examples with yarn start.)
• You've added a changeset if changing functionality. (Add one with yarn changeset add.)

[changeset-bot]

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Latest commit: 133b192

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