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>

tests/x-localip.bats

@@ -0,0 +1,7 @@
+#!/usr/bin/env bats
+
+@test "x-localip prints version" {
+  run bash local/bin/x-localip --version
+  [ "$status" -eq 0 ]
+  [[ "$output" == "x-localip version"* ]]
+}