Allow lint-scripts.sh to be run locally

[apolopena]

Currently it is not possible lint-starter on a local machine outside the gitpod platform.
Linting the scripts is an important step when developing gitpod-laravel-starter outside of Gitpod.

Change:

path() {
  echo "$GITPOD_REPO_ROOT/.gp"
}

To

path() {
  [[ -z $GITPOD_REPO_ROOT ]] && GITPOD_REPO_ROOT="$(pwd)"
  echo "$GITPOD_REPO_ROOT/.gp"
}