Fix comments for IME

[budnix]

Context

The PR fixes the comments functionality, which does not work correctly when the typed values come from the IME. A new hook (beforeCompositionStart) had to be introduced to fix the issue. The hook allows implementing custom handling or blocking of core logic when the IME is used.

How has this been tested?

I tested the changes locally, and I covered the fix and a new hook with tests.

Types of changes

• New feature or improvement (non-breaking change which adds functionality)

Related issue(s):

1. fixes https://github.com/handsontable/dev-handsontable/issues/2281

Affected project(s):

• handsontable
• @handsontable/angular

Checklist:

• I have reviewed the guidelines about Contributing to Handsontable and I confirm that my code follows the code style of this project.
• I have signed the Contributor License Agreement
• My change requires a change to the documentation.

[codesandbox-ci]

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Latest deployment of this branch, based on commit e0ddfe8:

Sandbox	Source
handsontable-pr-javascript-demo	Configuration
handsontable-ts-demo	Configuration
handsontable-pr-react-demo	Configuration

[github-actions]

Launch the local version of documentation by running:

npm run docs:review 0f433845196e1dc01e6f314dd42e15d5aa5f5277