fix(web): actually serve the manifest and pwa files when running go server

bskyweb/cmd/bskyweb/server.go

···
 		e.GET("/robots.txt", echo.WrapHandler(staticHandler))
 	}
 
+	// pwa files
+	e.GET("/manifest.json", echo.WrapHandler(staticHandler))
+	e.GET("/pwa-512.png", echo.WrapHandler(staticHandler))
+	e.GET("/pwa-192.png", echo.WrapHandler(staticHandler))
+
 	e.GET("/iframe/youtube.html", echo.WrapHandler(staticHandler))
 	e.GET("/static/*", echo.WrapHandler(http.StripPrefix("/static/", staticHandler)), func(next echo.HandlerFunc) echo.HandlerFunc {
 		return func(c echo.Context) error {

bskyweb/templates/base.html

···
 
   <link rel="preload" as="font" type="font/woff2" href="{{ staticCDNHost }}/static/media/InterVariable.c504db5c06caaf7cdfba.woff2" crossorigin>
 
+  <link rel="manifest" href="/manifest.json" />
+
   <style>
     /**
      * Minimum styles required to render splash.