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-git-largest-files.py.md

@@ -0,0 +1,21 @@
+# x-git-largest-files.py
+
+Lists the largest files in a git repository.
+
+```bash
+x-git-largest-files.py [options]
+```
+
+Options:
+
+- `-c NUM` – number of files to show (default: 10)
+- `--files-exceeding N` – list files larger than N KB
+- `-p` – sort by on-disk size instead of pack size
+
+## Example
+
+```bash
+x-git-largest-files.py -c 5
+```
+
+<!-- vim: set ft=markdown spell spelllang=en_us cc=80 : -->