Make ROOT_DIR available in Dotfile

The ROOT_DIR variable is set to the directory the Dotfile is in.

src/lib/internals/execute-dotfile.sh

@@ -4,6 +4,8 @@ execute-dotfile() {
   locate-target
   if [ "$?" != "0" ]; then return 1; fi
 
+  ROOT_DIR="$(dirname "$DOTFILE")"
+
   eval "$dotfile_source"
   return $?
 }