Parachain content

[nuke-web3]

I am opening this issue to gather insights into what needs to be added to our devhub as it relates to parachains.
Please let's use this to discuss what we think is needed, and priorities for this.

Present content includes the HTG section, and the cumulus workshop. But there is a general lack of information on the devhub as it relates to cumulus, parachains, and the nuances that make it different than solo-chain development with substrate.

A few topics that I see as critically needed:

• Collator selection (options beyond the template)
• Reading data from the relay chain state
  • Like randomness on chain (Support custom storage proof from the relay-chain paritytech/polkadot-sdk#82)
• Don't validate a block announcement when syncing paritytech/cumulus#150
• Bridging (https://github.com/paritytech/parity-bridges-common/) and compare/contrast with XCMP
  • Workshop video: https://www.youtube.com/watch?v=rrpDBvac7gI
• Ensure the whole repo is free of TODOs and FIXMEs, or open a new issue Fix storage_append paritytech/cumulus#158

... I am sure there is more.

What do you think should be added, and what takes priority?