feat: publish versioned image tags to dockerhub (sourcegraph#52)

Author: nejch

.github/workflows/scip-release.yml

@@ -31,4 +31,7 @@ jobs:
         with:
           file: Dockerfile.autoindex
           push: true
-          tags: sourcegraph/scip-python:autoindex
+          tags: |
+            sourcegraph/scip-python:autoindex
+            sourcegraph/scip-python:latest
+            sourcegraph/scip-python:${{ github.ref_name }}