Run tests on PR, add docs

.github/workflows/tests.yml

@@ -0,0 +1,19 @@
+name: Tests
+
+on:
+  pull_request:
+    branches:
+      - master
+  push:
+    branches:
+      - master
+
+jobs:
+  prove:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Install Perl::Critic
+        run: sudo apt-get update && sudo apt-get install -y libperl-critic-perl
+      - name: prove -lr
+        run: prove -lr

t/README.md

@@ -132,8 +132,9 @@ yourmodule/
     run-tests.t    # see nftables/t/run-tests.t for the WEBMIN_CONFIG / tmpdir setup
 ```
 
-A module's tests are reachable from `prove -lr t` at the root via the
-`-r` recursive walk.
+A module's tests are reachable from `prove -lr` at the repo root (no
+path arg, so the recursive walk starts at the cwd). `prove -lr t` only
+walks within `t/` and will miss `<module>/t/`.
 
 ## Caveats