nvm: check $XDG_CONFIG_HOME/nvm for an nvm installation

Closes #7807
Co-authored-by: Marc Cornellà <marc.cornella@live.com>

plugins/nvm/nvm.plugin.zsh

-# Set NVM_DIR if it isn't already defined
-[[ -z "$NVM_DIR" ]] && export NVM_DIR="$HOME/.nvm"
+# See https://github.com/nvm-sh/nvm#installation-and-update
+if [[ -z "$NVM_DIR" ]]; then
+  if [[ -d "$HOME/.nvm" ]]; then
+    export NVM_DIR="$HOME/.nvm"
+  elif [[ -d "${XDG_CONFIG_HOME:-$HOME/.config}/nvm" ]]; then
+    export NVM_DIR="${XDG_CONFIG_HOME:-$HOME/.config}/nvm"
+  fi
+fi
 
 # Don't try to load nvm if command already available
 which nvm &> /dev/null && return