Document default value for [SUBGRAPH-MANIFEST] in the CLI

[PaulRBerg]

When running graph build or graph deploy in the CLI, it is possible to omit the value for the [SUBGRAPH-MANIFEST] argument because the default value subgraph.yaml is used.

However, this behavior is nowhere to be found in the --help output:

bun run graph deploy --help
 ›   Warning: @graphprotocol/graph-cli update available from 0.96.0 to 0.97.0.
Deploys a subgraph to a Graph node.

USAGE
  $ graph deploy [SUBGRAPH-NAME] [SUBGRAPH-MANIFEST] [-h] [-g <value>] [--deploy-key <value> | --access-token <value>] [-l <value>] [-i
    <value>] [--ipfs-hash <value>] [--headers <value>] [--debug-fork <value>] [-o <value>] [--skip-migrations] [-w] [--network <value>]
    [--network-file <value>]

Or:

bun run graph build --help
 ›   Warning: @graphprotocol/graph-cli update available from 0.96.0 to 0.97.0.
Builds a subgraph and (optionally) uploads it to IPFS.

USAGE
  $ graph build [SUBGRAPH-MANIFEST] [-h] [-i <value>] [-o <value>] [-t wasm|wast] [--skip-migrations] [-w] [--network <value>]
    [--network-file <value>]