update act to v0.2.34

this also required updating the action image to node16

this is a potentially breaking change, so I don't think we want this plugin
image to be tagged 'latest' if/when this change is merged to main

I have also updated the drone pipeline to only publish the image on tag
events, so if we give a proper tag (maybe 2.0.0) this updated plugin image
will be available as plugins/github-actions:2 which will not break existing
pipelines pulling latest

.drone.yml

@@ -15,6 +15,15 @@ steps:
   - go test ./...
   - sh scripts/build.sh
 
+- name: publish (dry run)
+  image: plugins/docker
+  pull: if-not-exists
+  settings:
+    dry_run: true
+    repo: plugins/github-actions
+    auto_tag: true
+    dockerfile: docker/Dockerfile.linux.amd64
+
 - name: publish
   image: plugins/docker
   pull: if-not-exists
@@ -25,4 +34,7 @@ steps:
     username:
       from_secret: docker_username
     password:
-      from_secret: docker_password
+      from_secret: docker_password
+  when:
+    event:
+    - tag