fix(flow-config-parser): support module.name_mapper.extension remap

[ncthuc2004]

Summary

• add first-class support for module.name_mapper.extension in flow-config-parser
• convert extension shorthand into regex-based remappers so imports like icons/check.png can be redirected predictably
• apply extension remappers in remapModule() after explicit module.name_mapper rules
• add tests that verify both css and png extension remap behavior

Why

Issue #27 is about type imports not resolving to expected .js.flow style definitions. This patch improves module remapping parity with Flow config shorthand so type-import rewrites can reliably target definition files.

Validation

• updated packages/flow-config-parser/src/__tests__/flowConfigParser.test.js
• parser behavior now remaps extension-based imports through config shorthand

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IssueHunt Summary

Referenced issues

This pull request has been submitted to:

• #27: Types not resolving to .js.flow files

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