Logging improvements

In this release, errors are now output to STDERR by default, and it's possible to configure whether to log static requests and send 404 errors to the error log.

What's Changed

• feature: configure logging of static requests and 404
• tweak: output errors to error stream
• Add JetBrains sponsorship to README with H1 heading by @g105b in #46

Full Changelog: v1.1.5...v1.1.6