adding GitHub option on our website

[h4l0gen]

Adding GitHub on main page and main menu.
This PR will solve Add a more explicit Github link to the website #28 issue.
fixes #28

[h4l0gen]

This will not only solve issue related to specification repo, It will provide clear guidance to users to join TUF GitHub directly from website. After its merging, I will attach this with my contributing page PR. Please take a look
Thank you!

[joshuagl]

Thanks for the contribution! I'm not a fan of this being the most prominent link on the website, I think it's better suited as a child of the Community menu. WDYT?

[h4l0gen]

SGTM 👍, One more suggestion, IMO we should add GitHub and Slack icon in footer.html and that will redirect users to contribute->GitHub and slack channel, instead of giving GitHub option on home page. By this we can remove slack submenu and GitHub and slack is approachable from every page of website. WDYT? @joshuagl

[h4l0gen]

@joshuagl with these changes website looks maintained to me. Please provide your feedback. Publication and project weight orders are same, so i corrected them here

[joshuagl]

Thanks for fixing the publications and projects weightings.

I'm not convinced having chat and GitHub links in the footer is that noticeable given how busy the footer already is and how they are squashed together (at least here in Firefox 126):

Let's at least keep the chat link in the community menu.

[h4l0gen]

Okay, @joshuagl what about putting GitHub option as box on home page as I did initially, or GitHub is good at footer?

IMO we should keep GitHub and slack in footer also and drop idea of putting GitHub on main page in Box. WDYT?