docs: add Modern.js Module migration docs

[YanPes]

Summary

This PR adds documentation regarding the migration of Modern.js Module projects to Rslib

Related Links

closes: #377

Checklist

• Tests updated (or not required).
• Documentation updated (or not required).

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1 out of 2 committers have signed the CLA.

✅ Timeless0911
❌ yannik.peschke

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[YanPes]

signed the CLA

[Timeless0911]

Awesome work! We can use this migration document for now, and we will complete a more complete configuration map and provide codemod in the future.

[Timeless0911]

signed the CLA

@YanPes The CI state is still blocked, can you confirm it?

[YanPes]

signed the CLA

@YanPes The CI state is still blocked, can you confirm it?

@Timeless0911 : Yes I have signed it. Here is the "proof". I checked locally. It seems I accidentally did not overwrite my git config user.email for the forked repo and pushed my changes with my business email instead which is already linked to a business account. Cannot bind it to this one.

Will not happen a second time - i adapted the configs. Sorry for the inconvenience

[Timeless0911]

@YanPes Haha, never mind, I always forgot to switch accounts when I re-clone the repository too. I can just skip the cla CI check for this PR. Thank you!