Implement `toMatchInlineDiffSnapshot` custom matcher

[domsli]

See #330 for why we want this change.

I manually checked the overall change locally by trying the matcher in a separate project: https://github.com/domsli/snapshot-inline-diff-test-app/blob/master/src/App.test.tsx

Some things to note on what was checked:

• Snapshots are generated when they don't exist
• Snapshots will fail if they are incorrect
• Snapshots update with the -u flag

[domsli]

@thymikee is this something you would be able to look at?