This commit introduces `mike` [1] as a documentation versioning plugin.

The documentation in the release-0.1 branch will appear under a `v0.1`
version. This version will also be the latest and default documentation
version until FuseML 0.2 is released.

[1] https://github.com/jimporter/mike

The mike tool needs the github user configuration to be set up. It
also needs a full git checkout to be able to compute the composed
documentation from multiple branches (see jimporter/mike#49).

[0.1] Add support for documentation versioning

(cherry picked from commit c297b10)

[0.1] Add banner warning users about old or devel documentation version

The JS script was looking for the versions.json file in the wrong
location.

(cherry picked from commit 7dbf9bb)

[0.1] Fix version warning banner

Stop publishing the docs from the 0.1 release as default/latest in
preparation of the 0.2 release.

[0.1] Stop using latest for 0.1 docs