fuzzing harnesses

Hi,

I created fuzzing harnesses which achieve great coverage on the project (and had 0 findings with ubsan + asan enabled).

```
Filename Regions Missed Regions Cover Functions Missed Functions Executed Lines Missed Lines Cover Branches Missed Branches Cover
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
picohttpparser.c 636 20 96.86% 14 0 100.00% 449 3 99.33% 332 22 93.37%
-
```
Would like them added to the repository? They work with AFL++, libafl and libfuzzer.

Start with picohttpparser.c and the harnesses described in the issue, then determine how AFL++, libafl, and libfuzzer inputs would be incorporated into the repository. Done means the harnesses are added with a repeatable build or run path and retain the reported sanitizer and coverage results.

Written by the indexing model from the issue text.