"Deep blame" for squashed commits #2876

1. Visit https://github.com/sindresorhus/refined-github/blame/0ca864af6da9cac9f503e4abd0c58b60fbe1abc6/source/features/link-to-file-in-file-history.tsx#L29

There's no blame specifically for that line, there's only a big blame block. However if you follow the PR's link, (5 clicks and 4 page loads later) you'll end up on this page:

https://github.com/sindresorhus/refined-github/blame/a2f6e93ca789d2b0677e152bc28d35d4a4180175/source/features/link-to-file-in-file-history.tsx#L34

This feature would need I think:

1. On blame page, add "deep blame this commit" button on each commit that has a PR link in its title
2. When the button is clicked, it has to query the API to get the PR's latest commit (user will be shown a loading icon)
3. Redirect to that commit

Step 2 should (if possible) verify that the linked PR is effectively the one that was squashed, and not just a randomly-linked PR.