Describe the problem

Some users have had errors with the validator processing their GTFS feeds because their websites are not set up to either 1) process requests with custom user agents or 2) process any requests from non-browser sources.

We want to be explicit about what our user agent header contains for debugging and logging purposes.

Suggest a fix or an alternative

Document the changes made in https://github.com/MobilityData/gtfs-validator/pull/1633/files in the "Using web-based validator" heading of the README