v1.8 docs need to be cut

[voisey]

If I go to the magma homepage, I still get the docs for 1.7.0 instead of 1.8.0. As was done in this PR for 1.7.0, we need to cut the new docs by creating a new folder in docs/docusaurus/versioned_docs. Docs changes that have been added since 1.8.0 should not be added unless they are changes that should be backported.