Improve celestia-appd init --help docs

[rootulp]

$ celestia-appd init --help
Initialize validators's and node's configuration files.

Usage:
  celestia-appd init [moniker] [flags]

Flags:
      --chain-id string             genesis file chain-id, if left blank will be randomly created
  -h, --help                        help for init
      --home string                 node's home directory (default "/Users/rootulp/.celestia-app")
  -o, --overwrite                   overwrite the genesis.json file
      --recover                     provide seed phrase to recover existing key instead of creating
      --staking-bond-denom string   genesis file staking bond denomination, if left blank default value is 'stake'

Global Flags:
      --log_format string   The logging format (json|plain) (default "plain")
      --log_level string    The logging level (trace|debug|info|warn|error|fatal|panic) (default "info")
      --trace               print out full stack trace on errors

Ideas for how to improve:

1. Explain [moniker]
2. Potentially include an example usage with moniker and --chain-id populated (especially for testnets)
3. Does this command actually generate separate files for validators and nodes? Can it instead say something like: "Initialize the configuration files for a Celestia consensus node"