feat: button to message matrix contact

[AntKru]

Closes #4700

Adds a button next to matrix entries which links to the conversation:
The entry @test:test.com will link to matrix:u/test:test.com?action=chat

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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[hamza221]

@GretaD does Matrix exist as a prop already ?

[GretaD]

yes: https://github.com/nextcloud/contacts/blob/main/src/models/rfcProps.js#L200

[hamza221]

mb, I was looking at social networks