Update the README to include all necessary information about the repo

[TarikGul]

Things to ensure:

• supported node versions
• release information
• browsers that are compatible
• docs on xcm structure (What does each direction mean)
• any edge cases that need to be covered.
• how does injection work.

[acatangiu]

Bumping this - any parachain team coming to this repo can't easily figure out what it does, how it helps them, how they can contribute their own para's info, etc