allow triggering workflows manually (#17)

.github/workflows/test.yml

@@ -1,5 +1,6 @@
 name: Test
 on:
+  workflow_dispatch:
   push:
     branches:
       - master

.github/workflows/update-langs.yml

@@ -1,5 +1,6 @@
 name: Update supported languages
 on:
+  workflow_dispatch:
   schedule:
     #        ┌───────────── minute (0 - 59)
     #        │ ┌───────────── hour (0 - 23)