Document SOP for updating go version

[BigLep]

Every 6 months we update the go version. Lets have the SOP for how we do this.

I think this should be a new file in https://github.com/ipfs/kubo/tree/master/docs

[BigLep]

@hacdias @Jorropo : I'm hoping you can take this given having recently gone through this with 1.21.

Minimum: point to the set of PRs we had to do for 1.21 across Kubo and related projects (e.g., ipfs/ipfs-docs#1729 ).

Thanks