Allow real Echidna publishing runs from workflow_dispatch (#1850)

Specify the dry-run variable and pass it through to Echidna

.github/workflows/w3c-publish.yml

@@ -15,6 +15,10 @@ on:
   # Candidate Recommendation Snapshot).
   workflow_dispatch:
     inputs:
+      dry-run:
+        required: true
+        type: boolean
+        description: If set, Echidna will validate but not publish.
       w3c-status:
         required: true
         type: choice
@@ -60,7 +64,9 @@ jobs:
           W3C_ECHIDNA_TOKEN_CORE: ${{ secrets.W3C_ECHIDNA_TOKEN_CORE }}
           W3C_ECHIDNA_TOKEN_JSAPI: ${{ secrets.W3C_ECHIDNA_TOKEN_JSAPI }}
           W3C_ECHIDNA_TOKEN_WEBAPI: ${{ secrets.W3C_ECHIDNA_TOKEN_WEBAPI }}
-          ECHIDNA_DRYRUN: ${{ !(github.event_name == 'push' && github.repository == 'WebAssembly/spec' && github.ref == 'refs/heads/main') }}
+          ECHIDNA_DRYRUN: |-
+            ${{ (github.event_name == 'workflow_dispatch' && inputs.dry-run) ||
+                !(github.event_name == 'push' && github.repository == 'WebAssembly/spec' && github.ref == 'refs/heads/main') }}
       - name: Validate ${{ matrix.spec }} spec with Echidna
         if: env.W3C_USERNAME
         run: cd document && make -e -C ${{ matrix.spec }} WD-echidna