[Breaking Change!] [Test] Change and unify the extension of generated files.

[cristianoc]

Test a breaking change to the extension of generated files.

• Change the extension of generated files to .regen.js and .regen.tsx.

• The name becomes uniform across TypeScript and Flow.

• No need for a special webpack plugin to read .re.js files instead of .re files.

• No difference in instructions to specify the current file in bs.value with TypeScript or Flow/Untyped.

• Make it easier to e.g. grep generated files: *.regen.*.

#90

[cristianoc]

The name regen is a placeholder.
Another possibility is e.g. .gt.

[cristianoc]

Original suggestion from #86.

[ryyppy]

🙌 I would also like to throw in .gen.js as a shorter ext suggestion

[cristianoc]

There seems to be interest in a shorter extension.
Changed the PR to .gen.tsx and .gen.js.

[cristianoc]

Merged in version 1.0.0.