.github/workflows: enable manual dispatch for some workflows (#5929)

.github/workflows/docs.yml

@@ -1,7 +1,8 @@
 name: Documentation
-# This job builds and deploys documenation to github pages.
-# It runs on every push to master.
+# This job builds and deploys documentation to github pages.
+# It runs on every push to master, and can be manually triggered.
 on:
+  workflow_dispatch: # allow running workflow manually
   push:
     branches:
       - master

.github/workflows/e2e.yml

@@ -2,6 +2,7 @@ name: e2e
 # Runs the CI end-to-end test network on all pushes to master or release branches
 # and every pull request, but only if any Go files have been changed.
 on:
+  workflow_dispatch: # allow running workflow manually
   pull_request:
   push:
     branches:

.github/workflows/proto.yml

@@ -2,6 +2,7 @@ name: Protobuf
 # Protobuf runs buf (https://buf.build/) lint and check-breakage
 # This workflow is only run when a .proto file has been modified
 on:
+  workflow_dispatch: # allow running workflow manually
   pull_request:
     paths:
       - "**.proto"