Adds message support

[TiBiBa]

First, provide a one line summary of your changes in the Title of the PR

Now fill out the remainder of this template by replacing all italic content

Description

Changes in detail

For example: "Adds translations of levels 1 to 12 to Polish" (note the use of present tense!)

Fixes issue or discussion number

Always link the number of the issue or of the discussion that your pr concerns.

How to test

• If this is a UI change: describe how to run your code to see it in action. See this https://github.com/Felienne/hedy/pull/880#issue-1016304308 for an example
• If this is a language change: add a few tests showing the difference

Checklist Done? Check if you have it all in place using this list:*

• [ ] Describes changes in the format above (present tense)
• [ ] Links to an existing issue or discussion
• [ ] Has a "How to test" section

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