fix(ci): make it possible to trigger a release manually

cf "There are no relevant changes, so no new version is released" from https://github.com/adrienjoly/chrome-next-step-for-trello/actions/runs/4650283347/jobs/8229177797#step:5:41, after merging PR #163.

Author: adrienjoly

.github/workflows/ci.yml

@@ -7,6 +7,12 @@ on:
   pull_request:
     branches:
       - main
+  workflow_dispatch:
+    inputs:
+      job:
+        description: 'Job to run'
+        required: true
+        default: 'release'
 
 jobs:
   build: