feat: add bats tests, docs (#139)

* fix(test): ensure bats file list uses xargs

* docs(readme): use yarn for testing instructions

* fix(test): ensure pipelines fail properly

* docs(alias): fix table header

---------

Signed-off-by: Ismo Vuorinen <ismo@ivuorinen.net>

local/bin/x-open-ports.md

@@ -0,0 +1,19 @@
+# x-open-ports
+
+List listening ports using `lsof` or `ss`.
+
+## Usage
+
+```bash
+x-open-ports [--json]
+```
+
+- `--json` – output as JSON instead of Markdown
+
+## Example
+
+```bash
+x-open-ports --json
+```
+
+<!-- vim: set ft=markdown spell spelllang=en_us cc=80 : -->