Docs: Fix root project contributing links

[OliverDavey]

/contributing.md redirected users to /docs/contributing.md but the link was broken (missing file extension).

/README.md pointed users to /contributing.md so this has been updated to the new location /docs/contributing.md to eliminate an additional step

[sonarqubecloud[bot]]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[fgmacedo]

Hi @OliverDavey, how are you?

Unfortunately, the issue is a bit trickier. I reuse the README.md file in the build docs as the main page by including it via a relative parent folder reference.

That’s where the problem comes in: the links in README.md end up broken—either in the documentation or in GitHub’s markdown rendering. Fixing it for one environment breaks it in the other. I haven’t found a good solution yet, and this PR would currently break the docs build.

Maybe a solution is to keep the README.md compatible to the Github renderer and add a preprocessor to include docs/ for links when building the docs.