Feat/release queue (#1192)

* queue release workflow so only one release can run at one time

* wait for 20 mins for release to finish

Co-authored-by: TomPallister <tom@threemammals.com>

.circleci/config.yml

@@ -1,4 +1,6 @@
-version: 2.1
+version: 2.1
+orbs:
+  queue: eddiewebb/queue@1.5.0
 jobs:
   build:
     docker:
@@ -15,8 +17,13 @@ jobs:
 workflows:
   version: 2
   master:
-    jobs:
-      - release:
+    jobs:
+      - queue/block_workflow:
+          time: "20"
+          only-on-branch: master
+      - release:
+          requires:
+            - queue/block_workflow
           filters:
             branches:
               only: master