Add a rules to help with the .toMatchNamedSnapshot() matcher usage

[mrazauskas]

From jestjs/jest#14045 (comment)

The linked PR is about to add .toMatchNamedSnapshot() matcher to Jest. The matcher works similar to .toMatchSnapshot(), but requires setting snapshot name explicitly that allows snapshot testing in concurrent mode (details of the problem jestjs/jest#2180).

After the PR lands, eslint-plugin-jest could be helpful by adding these rules:

• no-duplicate-snapshot-names: show error if the same snapshot name was used twice in a test file
• prefer-named-snapshots: require to use .toMatchNamedSnapshot() matcher with test.concurrent (or always)

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This is just a note for discussion. No action required at the moment (;

[SimenB]

I think both of these rules sounds good. @G-Rath thoughts?

[G-Rath]

Yeah they sound reasonable (though I'd probably say go with prefer-snapshot-name to match nicely with prefer-snapshot-hint) - you could do prefer-snapshot-name with no-restricted-matchers, though that would be all or nothing and I guess it makes sense for us to tell people by default what to do when using concurrent

[mrazauskas]

The concurrent snapshots are now supported without adding new matcher (see jestjs/jest#14139). So the rules will not be needed.