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-multi-ping.md

@@ -0,0 +1,20 @@
+# x-multi-ping
+
+Multi-protocol ping helper supporting IPv4 and IPv6.
+
+## Usage
+
+```bash
+x-multi-ping [--loop] [--sleep=N] host1 host2...
+```
+
+- `--loop` – ping continuously
+- `--sleep` – seconds to wait between iterations
+
+## Example
+
+```bash
+x-multi-ping --loop --sleep=5 example.com
+```
+
+<!-- vim: set ft=markdown spell spelllang=en_us cc=80 : -->