Add new plugin unique, to check last messages

[8of]

Fixes https://github.com/aahnik/tgcf/issues/578

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[aahnik]

Hi hi @8of 👋 Thank you so much for your contribution...

Unfortunately the main branch is not up to date, with the major changes I have made.

Kindly create a new branch from the multx-01 branch and open a pull request to that branch.

I will try to review, test and merge that as soon as possible.

[8of]

PR will be re-created from another branch.