Static files compressed with brotli (`br_static=true`) will fail to be sent if uncompressed file doesn't exist

The checks whether or not the `*.br` compressed files exist are done in `StaticFileRouter::sendStaticFileResponse`, however if the original uncompressed file doesn't exist in the static file location then the request would be rejected much before that inside `StaticFileRouter::route` which checks for the existence of the original uncompressed file without the `.br` extension even tho the `*.br` file exists there. Doesn't it make more sense for those checks to be added inside the `route` function as well so that compressed files can be sent by request even if the uncompressed ones don't exist?