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-env-list.md

@@ -0,0 +1,21 @@
+# x-env-list
+
+Lists environment variables grouped by their prefix. Sensitive values
+are hidden by default.
+
+## Usage
+
+```bash
+x-env-list [options]
+```
+
+Use `--json` for machine readable output or specify
+`X_ENV_GROUPING` with a YAML file to override the default groups.
+
+### Example
+
+```bash
+X_ENV_GROUPING=~/env-groups.yaml x-env-list --json
+```
+
+<!-- vim: set ft=markdown spell spelllang=en_us cc=80 : -->