chore: lock jest peer dependency to version 26 or 27

[mxschmitt]

Fixes #794

I did it in a separate PR since more changes were required to make CI green.

[coveralls]

Pull Request Test Coverage Report for Build 2387390584

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+1.4%) to 96.226%

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Totals
Change from base Build 2387388913:	1.4%
Covered Lines:	106
Relevant Lines:	109

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💛 - Coveralls