Add Flow and document template init script, simplify args

[huntie]

Summary:

• Add Flow, switch from yargs to parseArgs (built-in to Node.js, Flow-safe).
• Document script via --help output (relevant ahead of reusing this script for local release testing).
• Relocate and add Flow to setup-verdaccio.js util, removing verdaccioStoragePath parameter (use verdaccio.yml as source of truth).

Also:

• Remove --reactNativeRootPath arg.
• Tweak other arg names.

Changelog: [Internal]

Differential Revision: D53484322

[facebook-github-bot]

This pull request was exported from Phabricator. Differential Revision: D53484322

[analysis-bot]

Platform	Engine	Arch	Size (bytes)	Diff
android	hermes	arm64-v8a	17,238,556	+4
android	hermes	armeabi-v7a	n/a	--
android	hermes	x86	n/a	--
android	hermes	x86_64	n/a	--
android	jsc	arm64-v8a	20,600,986	+7
android	jsc	armeabi-v7a	n/a	--
android	jsc	x86	n/a	--
android	jsc	x86_64	n/a	--

Base commit: 0575033f768447e69f085a3c7f20b00daedd2530 Branch: main

[facebook-github-bot]

This pull request has been merged in facebook/react-native@d243cd9ca9043a2fb93cfbd3a6d917a72493b385.