Styles error pages & adds dynamic content via Service Worker content injection. Creates an error layout that everything can extend for consistency. It shows the actual page status & a nice message. Adds for 503 (offline), 404, and 500 (generic error).

Refactors service worker’s default handler to do the 404 if the page wasn't found, and the catchHandler to fallback to a 500.html generic error page. This removes the unnecessary try/catch & also refactors the code a bit to make it more readable & digestible. Creates separate _errors directory and _static directory for better naming.

Bumps minor version