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/msgr.md

@@ -0,0 +1,20 @@
+# msgr
+
+Helper library for printing colorized log messages from shell scripts.
+
+## Usage
+
+```bash
+msgr <type> "message" [extra]
+```
+
+Message types include `ok`, `warn`, `err`, `run` and many more. The
+script is primarily sourced by other scripts.
+
+### Example
+
+```bash
+msgr ok "Installation complete"
+```
+
+<!-- vim: set ft=markdown spell spelllang=en_us cc=80 : -->