Finish up Templates document

[juangirini]

In docs/sdk/src/polkadot_sdk/templates.rs

TODOs

• in general, we need to make a deliberate choice here of moving a few key templates to this repo (nothing stays in substrate-developer-hub) and the everything else should be community maintained.
• rename substrate-node-template to substrate-basic-template, substrate-blockchain-template. node is confusing in the name. substrate-blockchain-template and cumulus-parachain-template go well together 🤝.

[nuke-web3]

Related to #26 - Looking at the template situation, the main tooling that is no longer maintained to update them on a polkadot release was https://github.com/paritytech/polkadot-sdk/blob/master/substrate/docs/node-template-release.md and the associated tooling https://github.com/paritytech/polkadot-sdk/blob/master/substrate/scripts/ci/node-template-release/src/main.rs that would need to be updated for the new SDK layout and CI, and I must be missing the companion CI for the cumulus parachain template.

paritytech/polkadot-sdk#186 is related as well, perhaps https://forum.polkadot.network/t/r0gue-reimagining-polkadot-development-with-pop/4938#pop-3 should be consulted in what they want to take on/take over?