Go wiki has moved https://github.com/golang/go/issues/61940. Wiki at
github.com/golang/go/wiki does not automatically move to go.dev/wiki
but says that wiki has moved.

I used the following shell one-liner to convert all links:

    $ find . -type f -print0 | xargs -0 sed -i 's,github.com/golang/go/wiki,go.dev/wiki,g'

To verify if they return 200:

    $ ag -a --nofilename -o 'https?.+wiki/.+?\b' | sort | uniq | xargs curl -sI
    HTTP/2 200
    (...)
    HTTP/2 200

since the vendor already stable since 1.5, update the doc to remove the note on vendor still experiment.

'.keep' files where committed early on to build a directory structure. Since then other files have been added to those directories, making
them unnecessary.