ci: add prettier workflow and refactor others

[romadryud]

Description

In this pr we have huge workflow refactoring, and it's only the start of it. I added a workflow with the name preview which will be the base workflow for preview all our changes, for now, preview has a prettier check and test workflows. In the near future preview will have all kinds of preview (docs, packages) and other tools like statistics and so on.

Prettier check can produce 2 variants of exit code for errors:

• 1 means there are format errors which can be fixed
• 2 means there are format errors which can not be fixed

If we have 1 variant, our bot will write a comment, "Looks like you forgot to run Prettier. Hopefully, you can automatically fix it by typing /prettify command." After sending, this command will trigger workflow to automatically run prettier and create a commit for it, and the original comment will be deleted by the bot.

If we have 2 variant, our workflow will fail and merging to the default branch will be impossible.

Closes #503 This depends on https://github.com/artalar/reatom/pull/685, after merging and rebase comments with command will work.

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[vercel[bot]]

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[romadryud]

Closing this one because we agreed to change the way we handle this automatically without typing the command in the comments. The new PR will be open soon.