Use safer append to hook function arrays (#8406)

Use add-zsh-hook to add functions to hooks. That way they won't be added again
when doing `source ~/.zshrc` multiple times.

Co-authored-by: Marc Cornellà <marc.cornella@live.com>

plugins/alias-finder/alias-finder.plugin.zsh

@@ -4,7 +4,7 @@ alias-finder() {
     case $i in
       -e|--exact) exact=true;;
       -l|--longer) longer=true;;
-      *) 
+      *)
         if [[ -z $cmd ]]; then
           cmd=$i
         else
@@ -43,4 +43,5 @@ preexec_alias-finder() {
   fi
 }
 
-preexec_functions+=(preexec_alias-finder)
+autoload -U add-zsh-hook
+add-zsh-hook preexec preexec_alias-finder