Added Leaf to Techempower benchmark

[joanhey]

TechEmpower/FrameworkBenchmarks#8347

Only plaintext and json.
Anybody want to add the db tests, in a Leaf way??

We need to add it with Eien Server too.

Also added using Adapterman:
https://github.com/joanhey/AdapterMan

I'll add the recipe for Leaf in Adapterman.
Later I'll add raw postresql, to test it with the async event loop in Workerman.

When the bench results are ready, I'll add here.

[joanhey]

https://www.techempower.com/benchmarks/#section=test&runid=473fbd63-e8ff-4082-919e-dd1be6f2a716&test=json