feat(nonblocking) implement non blocking mode for connections

[pankgeorg]

Towards making this work https://github.com/TechEmpower/FrameworkBenchmarks/pull/8370/files (more context)

I'm trying to remove any blocking calls from anywhere in the Julia Web stack. Though this may be minor, I think it's not a bad idea to have it around!

I'll have numbers regarding whether this works soon™️ 😅

TODO (@iamed2 please add more as you please)

• [ ] include in tests
• [ ] benchmark
• [ ] add guide in README.md

[alexandergunnarson]

An interested party here :) Curious what remains to be done and why it was abandoned.