DOC-2446: Added support for querying the state of the `mceTogglePlainTextPaste` command.

[FarzadHayat]

Ticket: DOC-2446

Site: Staging branch

Changes:

• TINY-10938 Release Note Entry: Added support for querying the state of the mceTogglePlainTextPaste command.
• Add mceTogglePlainTextPaste command to editor-command-identifiers.adoc

Pre-checks:

• [x] Branch prefixed with feature/<version>/, hotfix/<version>/, staging/<version>/, or release/<version>/
• [-] modules/ROOT/nav.adoc has been updated (if applicable)
• [-] Files has been included where required (if applicable)
• [-] Files removed have been deleted, not just excluded from the build (if applicable)
• [x] Files added for New product features, and included a release note entry.

Review:

• [ ] Documentation Team Lead has reviewed