Fix domain typo in the project readme

[HGStyle]

In the project readme, there is a little typo:
"- A fork in now under active development at https://gihub.com/llvm-fortran/fort.
See #22 for details."
It's wroten "gihub" instead of "github" (the T is missing)
Links of domain gihub.com redirects to ads which can be sometimes redirect to hacker ads.