ci: Add a dummy workflow

For the badge to work, we need to run at least one workflow for every
push, otherwise Ironforge will be sad.

Signed-off-by: Gergely Nagy <me@gergo.csillger.hu>

.forgejo/workflows/noop.yaml

@@ -0,0 +1,13 @@
+---
+name: Nothing.
+
+on:
+  push:
+
+jobs:
+  nothing:
+    runs-on: nixos-flakes
+
+    steps:
+      - name: no-op
+        run: echo "This is only here to make Ironforge happy."