Adds links to the README for roadmap, releases, RFCs. Fixes the help link (#22548)
Adds links to the README for roadmap, releases, RFCs. Fixes the help link (#22548)

Summary:
This PR only contains README updates.

1. Adds roadmap link
2. Adds releases repo link
3. Adds discussions and proposals repo link
4. Fixes the help link (pointed to abandoned forum)
Pull Request resolved: https://github.com/facebook/react-native/pull/22548

Differential Revision: D13372704

Pulled By: cpojer

fbshipit-source-id: 3c04d00ae08281298a851ddd6ec38ff67c6add30

pandiaraj44/react-native,javache/react-native,hammerandchisel/react-native,hammerandchisel/react-native,janicduplessis/react-native,janicduplessis/react-native,janicduplessis/react-native,facebook/react-native,exponent/react-native,exponentjs/react-native,javache/react-native,myntra/react-native,hammerandchisel/react-native,hoangpham95/react-native,janicduplessis/react-native,myntra/react-native,exponentjs/react-native,janicduplessis/react-native,hoangpham95/react-native,facebook/react-native,pandiaraj44/react-native,myntra/react-native,facebook/react-native,janicduplessis/react-native,hoangpham95/react-native,arthuralee/react-native,javache/react-native,exponentjs/react-native,exponent/react-native,arthuralee/react-native,arthuralee/react-native,myntra/react-native,exponent/react-native,pandiaraj44/react-native,myntra/react-native,janicduplessis/react-native,facebook/react-native,javache/react-native,hoangpham95/react-native,facebook/react-native,pandiaraj44/react-native,javache/react-native,hoangpham95/react-native,javache/react-native,pandiaraj44/react-native,arthuralee/react-native,exponentjs/react-native,hoangpham95/react-native,exponentjs/react-native,pandiaraj44/react-native,exponentjs/react-native,exponent/react-native,janicduplessis/react-native,facebook/react-native,exponentjs/react-native,myntra/react-native,pandiaraj44/react-native,hammerandchisel/react-native,hammerandchisel/react-native,javache/react-native,facebook/react-native,hammerandchisel/react-native,hammerandchisel/react-native,myntra/react-native,exponent/react-native,myntra/react-native,facebook/react-native,hoangpham95/react-native,facebook/react-native,arthuralee/react-native,exponent/react-native,exponent/react-native,exponent/react-native,hoangpham95/react-native,hammerandchisel/react-native,javache/react-native,myntra/react-native,exponentjs/react-native,pandiaraj44/react-native,javache/react-native