Link broken to awsome.md

[Guénolé de Cadoudal]

Hi,

I found a broken link while preparing my merge request
In page https://github.com/thomasdarimont/awesome-keycloak/blob/master/CONTRIBUTING.md
the link in

- Read [the awesome manifesto](https://github.com/sindresorhus/awesome/blob/master/awesome.md) and ensure your list complies.

should be changed to https://github.com/sindresorhus/awesome/blob/main/awesome.md.

The master branch has apparently been renamed as main

[Thomas Darimont]

Fixed thanks!