add fpath entry outside of plugin

compinit is called before plugins are loaded. to avoid having to call compinit
again after loading this plugin, suggest to set fpath outside of the plugin in
zshrc.

see also this issue zsh-users/zsh-completions#603

readme.md

@@ -19,7 +19,10 @@ Install it with your favourite zsh package manager, or clone it directly to your
 array in your `.zshrc` file:
 
 ```zsh
-plugins=(... zsh-asdf-direnv)
+export ASDF_DIR="$HOME/.asdf"
+fpath=(${ASDF_DIR}/completions $fpath)
+
+plugins = (... zsh-asdf-direnv)
 ```
 
 ## Usage

zsh-asdf-direnv.plugin.zsh

@@ -74,8 +74,6 @@ _zsh_asdf_direnv_install_asdf() {
 
 # source asdf and run the direnv hook, after adding completions to path
 _zsh_asdf_direnv_load() {
-  fpath=(${ASDF_DIR}/completions $fpath)
-
   # if specified only load the asdf wrapper, leaving the shims out of path
   if test "$ZSH_ASDF_DIRENV_LIBONLY" = "true"; then
     PATH="$PATH:$ASDF_DIR/bin"