Request wrapper

Migration guide

If you have ever discovered fetch.Request function before, replace it with fetch.Do
If you used json tags in the input of ToHandlerFunc, wrap the input with fetch.Request and access the needed data.
I removed DuplicateHeaders field from everywhere, just rely on Headers

What's Changed

• Downgrade to go1.21, Request wrapper by @glossd in #34

Full Changelog: v0.5.3...v0.6.0