ci: add `workflow_dispatch` to renovate and mirror

.forgejo/workflows/mirror.yml

@@ -1,6 +1,8 @@
 name: mirror
 
 on:
+  workflow_dispatch:
+
   schedule:
     - cron: '@daily'
 

.forgejo/workflows/renovate.yml

@@ -11,6 +11,7 @@ on:
       - 'renovate/**' # self-test updates
   schedule:
     - cron: '0 0/2 * * *'
+  workflow_dispatch:
 
 env:
   RENOVATE_DRY_RUN: ${{ (github.event_name != 'schedule' && github.ref_name != github.event.repository.default_branch) && 'full' || '' }}