We've made it easier to run a node with clearer, updated docs v2.21.0 ✨

- Added new articles:

a. Overview https://docs.nervos.org/docs/node/node-overview

b. Node Configuration https://docs.nervos.org/docs/node/node-config

c. Sync Options https://docs.nervos.org/docs/node/sync-options

- Reworked node setup docs for clarity (mainnet/testnet/devnet, light clients, public RPCs, etc.)

- Moved RPCs to the DApp section where they make more sense: https://docs.nervos.org/docs/dapp/rpcs

Release note: https://github.com/nervosnetwork/docs.nervos.org/releases/tag/v2.21.0