Introduce target directory option

This release:

1. Introduces a new CLI argument called output which specifies the output folder for all assets generated by create-pwa. This argument defaults to '' (empty string) which means the project root of the folder which contains the package.json file.
2. Fixes an issue with duplicated file names for the launch screens listed in the service worker file.
3. Updates all exported functions by adding a new argument - output which is the same as the CLI flag above. The only difference is that this argument is mandatory and does not have a default value.
4. Updates Github actions to use Node v18