docs: deploy using mike in CI

.github/workflows/build_docs.yml

@@ -17,5 +17,5 @@ jobs:
         with:
           key: ${{ github.ref }}
           path: .cache
-      - run: pip install mkdocs-material
+      - run: pip install mkdocs-material mike
-      - run: mkdocs gh-deploy --force
+      - run: mike deploy --push latest

Makefile

@@ -9,4 +9,4 @@ clean:
 	git clean -Xdf
 
 preview_site:
-	mkdocs serve
+	mike serve