Run mike set-default on release deployment (#178)

Looks like mike deployment won't stick without the set-default call

.github/workflows/publish-release-docs.yml

@@ -20,3 +20,4 @@ jobs:
                   git config user.name github-actions
                   git config user.email github-actions@github.com 
                   mike deploy --push --update-aliases ${{ github.event.release.name }} latest
+                  mike set-default --push latest