Git URLs in Markdown reports and diffs

[matejchalk]

The CLI need can improve in UX when we link the report source file issues to the related file. If we click the link alter we should either open up the file locally in our IDE or jump to the github repository, depending on the usage.

This issue is a follow-up to #148

Comparison Report:

• [x] commits in report-diff.md summary and report.md About section should link to web URL of given commit (using SHA)

Report:

• [ ] #748
  • [ ] #722
  • [x] #745

Implementation details:

• PR1 - Models and utils
• PR2 - IDE linking #722
• PR3 - Github linking #745