feat(fluxcd): add completion for flux (#11350)

plugins/fluxcd/README.md

@@ -0,0 +1,9 @@
+# FluxCD plugin
+
+This plugin adds completion for [FluxCD](https://fluxcd.io), an open and extensible continuous delivery solution for Kubernetes. Powered by GitOps Toolkit.
+
+To use it, add `fluxcd` to the plugins array in your zshrc file:
+
+```zsh
+plugins=(... fluxcd)
+```