cmd/deploy: update usage string

General MR

Summary

Update the deploy usage string with a couple more examples and fix typos.

Relevant logs/screenshots

Before

Examples:
  # Deploy big bang product to your cluster
  bbctl deploybig bang
  # Deploy bigbang to a k3d development cluster
  bbctl deploybig bang --k3d

After

Examples:
  # Deploy big bang product to your cluster
  bbctl deploy bigbang
  
  # Deploy bigbang to a k3d development cluster
  bbctl deploy bigbang --k3d
  
  # Deploy bigbang with a helm overrides file. All arguments after -- are passed to the underlying helm command
  bbctl deploy bigbang -- -f ../overrides/values.yaml

Linked Issue

N/A

Upgrade Notices

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