Fixes #1375: Clarify steps to reach Github issues

[heatherbooker]

Fixes #1375 -

• Add octocat github button icon
• Change wording
• Make keyboard hint only visible on screens of width > 40em

Screenshots:

Desktop:

Mobile:

This fix, when hovering over the octocat, does not change color, unlike #1408 !

[zoepage]

The changes look good to me. Just all the tests are failing. Will check again in the morning. :)

[miketaylr]

Just all the tests are failing. Will check again in the morning. :)

This is a bi-product of how our testing setup works. Forks don't have access to Travis secrets, so they either can't pass the auth tests, or hit rate limits for the non-auth tests.

(Part of this Outreachy round is to find a good solution for forked contributors!)

[zoepage]

@miketaylr ah, thanks for the info :)

Cool, so let's merge then :)