feat(transformers): add path-mapping custom AST transformer

[ahnpnl]

Summary

• Add path mapping custom AST transformer and expose it as a public transformer. This transformer can help user to avoid using moduleNameMapper.

• Adjust documentation for usage.

For now, it can be opt-in/out. If it’s stable and users want it as default, we can add it to default transformer set later

Test plan

Added unit tests and e2e tests

Does this PR introduce a breaking change?

• Yes
• No

Other information

N.A.

[coveralls]

Pull Request Test Coverage Report for Build 5816

• 56 of 58 (96.55%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.001%) to 92.937%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/transformers/path-mapping.ts	56	58	96.55%

Totals
Change from base Build 5808:	-0.001%
Covered Lines:	1123
Relevant Lines:	1162

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💛 - Coveralls