make it obvious that forking is easy

[cben]

Meta issue for lower barrier to entry:

• "fork this on github" or similar
• CONTRIBUTING.md
• easy deploy - Implement Netlify Button #76
• an easy way to at least provide feedback without github account

[cben]

Configured issue submission without GH user at https://gitreports.com/issue/cben/mathdown

Not yet linked from UI, not sure how I'd like top bar to look.
Given enough space, probably something like this:

[:speech_balloon: feedback] [:octocat: dev]

In ideal world, [dev] leads to (1) github or CONTRIBUTING.md (emphasis on ease of running a fork), (2) issues (3) current version, test results etc (4) git graph of recent changes (GH network?). In ideal² world, one can click any version to use it.
In practice, [dev] -> CONTRIBUTING.md is OK as entry point for power users.

[feedback] ideally lets one type within the app but link to Gitreports (which links power users to github issues) is OK as entry point.

Given less space, e.g. mobile, I'd have icon only + [feedback] button leading to Gitreports (which again can link to github).

[cben]

• Provide link (and/or header?) to the exact source version that is running.
  This would IIUC be a legal requirement if I were using Affero GPL; I'm not but it is a desired quality in hosted free software.