feat(pwa): add service-worker + webmanifest for each podcasts to have them install on devices

- configure service-worker using vite-plugin-pwa
- refactor Image entity to generate images of
different types based on size config
- add requirement for webp library for php gd to generate webp
images for instance
- add action to regenerate all instance images for eventual Images config
changes
- enhance google lighthouse metrics for pwa