feat(arduino-cli): add completion plugin (#12522)

plugins/arduino-cli/README.md

@@ -0,0 +1,8 @@
+# Arduino CLI plugin
+
+This plugin adds completion for the [arduino-cli](https://github.com/arduino/arduino-cli) tool.
+To use it, add `arduino-cli` to the plugins array in your zshrc file:
+
+```zsh
+plugins=(... arduino-cli)
+```