Cut 4.0 release

[yurrriq]

Depends on #93, at least. This is just a reminder for now.

[paulo-ferraz-oliveira]

@tsloughter, this is now around 4 years old 😄 I love my Elli and would like to see a 4.0 too. Anything I can do to help move it forward? Triage some more issues, fix some more stuff, close some more issues (?)

[tsloughter]

Do you know what the breaking changes are that make this 4.0?

[paulo-ferraz-oliveira]

I can look at the commits since the last release.

Edit: fwiw, 3.3.0...main.

[paulo-ferraz-oliveira]

This is what I found:

• record req now has field original_headers (was parsed_headers during dev.)
  • this is mentioned in the CHANGELOG
• header names are downcased (though this is most likely not breaking)
• the min. supported OTP bumped to 24+