[Document Request] Add a migration guide for byebug users

[st0012]

What

1. Add a document docs/migrate_from_byebug.md as the migration guide for byebug users.
2. Add a link to it in the readme

Content

• It should list command comparisons, especially around step debugging, to help users learn what's changed or not changed.
  • Preferably using markdown table for this instead of a separate page to optimize reader's experience.
• It should also emphasize the features that're unique to the debugger as an attraction.

Why

Based on the latest Rails community survey, byebug has 30% of the market share vs debugger's 10%. Given that byebug and the debugger share the same user base, a migration guide should help speed up the adoption.

Additional context

• I know there's already a debug command comparison sheet. It'll be a nice supporting material but it's not specific for byebug. So I think it can't replace the migration guide I mentioned above.
• If there's no objection on this idea, I'll work on it.

[ko1]

I don't have objection.

Some points:

• byebug has still advantages so I don't think all users should not migrate from byebug if users feel byebug is enough. Showing both advantages seems important and user can choose their own favorite.
• If it is written in a blog post, it is easy to manage by @st0012 and the author is clear. I'm happy to link to the post. If doc is in the repository, I will check the contents.

[st0012]

I've written this post as suggested 😄 It also mentions a few points on "why users should not migrate". But I think the migration should be beneficial in general.

[ko1]

Thank you, could you give me a PR to merge this link in README?