implement manual workflow trigger

.forgejo/workflows/renovate.yaml

@@ -1,6 +1,14 @@
 on:
+  workflow_dispatch:
+    inputs:
+      dryRun:
+        description: Dry Run
+        default: "false"
+        required: false
   schedule:
     - cron: '*/30 * * * *'
+env:
+  RENOVATE_DRY_RUN: "${{ inputs.dryRun == true }}"
 jobs:
   renovate:
     name: Renovate