add readme fot git-flow-avh

plugins/git-flow-avh/README.md

@@ -0,0 +1,12 @@
+# git-flow (AVH Edition) plugin
+
+This plugin adds completion for the [git-flow (AVH Edition)](https://github.com/petervanderdoes/gitflow-avh).
+The AVH Edition of the git extensions that provides high-level repository operations for [Vincent Driessen's branching model](https://nvie.com/posts/a-successful-git-branching-model/).
+
+The git-flow tool has to be [installed](https://github.com/petervanderdoes/gitflow-avh#installing-git-flow) separately.
+
+To use it, add `git-flow-avh` to the plugins array in your zshrc file:
+
+```zsh
+plugins=(... git-flow-avh)
+```