Allow PROPPATCH method

This only tells chi to pass those requests to the regular handler. It is
not really handled well in go-webdav so far (work in progress).

cmd/tokidoki/main.go

@@ -100,6 +100,7 @@ func main() {
 
 	for _, method := range []string{
 		"PROPFIND",
+		"PROPPATCH",
 		"REPORT",
 		"MKCOL",
 		"COPY",