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/a.md

@@ -0,0 +1,29 @@
+# a
+
+Encrypt or decrypt files and directories using `age` and your GitHub SSH keys.
+
+## Usage
+
+```bash
+a encrypt <file|dir>
+a decrypt <file.age|dir>
+```
+
+Options:
+
+- `-v`, `--verbose` – show log output
+
+Environment variables:
+
+- `AGE_KEYSFILE` – location of the keys file
+- `AGE_KEYSSOURCE` – URL to fetch keys if missing
+- `AGE_LOGFILE` – log file path
+
+## Example
+
+```bash
+a encrypt secret.txt
+a decrypt secret.txt.age
+```
+
+<!-- vim: set ft=markdown spell spelllang=en_us cc=80 : -->