Fix multiple typo in readme
Fix multiple typo in readme

Also removes mentioning of branch `clang`.
The approach with `libclang` is too dependent on a particular compiler

netheril96/StaticJSON,rsy96/autojsoncxx,netheril96/StaticJSON,vitalyisaev2/autojsoncxx,netheril96/StaticJSON,coldze/autojsoncxx,rsy96/autojsoncxx,netheril96/autojsoncxx,vitalyisaev2/autojsoncxx,netheril96/autojsoncxx,coldze/autojsoncxx