Register WebDAV-specific HTTP methods with chi

Otherwise the router will return 405 before the request makes it to our
middleware.

cmd/tokidoki/main.go

@@ -29,6 +29,9 @@ func main() {
 		os.Exit(1)
 	}
 
+	chi.RegisterMethod("PROPFIND")
+	chi.RegisterMethod("REPORT")
+	chi.RegisterMethod("MKCOL")
 	mux := chi.NewRouter()
 	mux.Use(middleware.Logger)