Document how existing migrated repo consumers update to go-libipfs

[BigLep]

👋 If wondering how update to use boxo from another ipfs/* repo that is no longer maintained, read here...

PLACEHOLDER TODO - this text will get filled in with more details once this issue is completed, likely just pointing to to-be-created docs. This is relevant since "not maintained messaging" points here.

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Done Criteria

There are docs that state the steps someone would take for upgrading to go-libipfs for any existing dependencies they had of repos that have been moved into go-libipfs.

Why Important

1. Ease the burden for those impacted by the transition.
2. Ensure maintainers are thinking about the experience of those impacted by this transition.

Notes

1. It should be clear what repos have moved over.
2. If there is tooling (e.g., Tooling to minimize impact on those updating to boxo #181), that should be linked to.

[BigLep]

@guseggert : do you have thoughts on where these docs will live? Will we have a md file under docs? docs/how_to_switch_to_boxo.md ?

[guseggert]

I've added documentation on how to migrate in this PR: #243