GH957 GH1010: Enhance docs for DotNetCore and GitReleaseManager aliases.

[luisgoncalves]

This fixes #957 and #1010. It's my first contribution; let me know if everything is OK.

[dnfclas]

Hi @luisgoncalves, I'm your friendly neighborhood .NET Foundation Pull Request Bot (You can call me DNFBOT). Thanks for your contribution!

In order for us to evaluate and accept your PR, we ask that you sign a contribution license agreement. It's all electronic and will take just minutes. I promise there's no faxing. https://cla2.dotnetfoundation.org.

TTYL, DNFBOT;

[gep13]

@luisgoncalves this looks great to me! Thank you for the contribution! Are you in a position to sign the CLA that is linked above? If you can do that, I will go ahead and get this merged.

[dnfclas]

@luisgoncalves, Thanks for signing the contribution license agreement so quickly! Actual humans will now validate the agreement and then evaluate the PR.

Thanks, DNFBOT;

[luisgoncalves]

@gep13 done!

[gep13]

@luisgoncalves perfect! 😄