Add workflow_dispatch input

.github/workflows/pelican.yml

@@ -4,8 +4,18 @@ on:
   push:
     branches: ["main"]
   workflow_dispatch:
+    inputs:
+      deploy:
+        required: false
+        default: true
+        description: "Whether to deploy the site. If true then build the site and deploy it. If false then just test that the site build's successfully but don't deploy anything."
+        type: boolean
   workflow_call:
 jobs:
+  Debug:
+    runs-on: ubuntu-latest
+    steps:
+      - run: echo "${{ inputs.deploy }}"
   Deploy:
     uses: seanh/pelican/.github/workflows/github_pages.yml@pelican_decouple_build_workflow-single-file
     permissions: