[Issue #63] Implement cg init command

[widal001]

Summary

Implements the cg init command for the CLI.

• Fixes [CLI] Create cg init command #63
• Time to review: 5 minutes

Changes proposed

What was added, updated, or removed in this PR.

• Implements the cg init command to call tsp init under the hood
• Updates the --list flag to read template options directly from the hosted template JSON
• Removes --dir as an option for the command since tsp init doesn't currently support custom output directories

Context for reviewers

Testing instructions, background context, more in-depth details of the implementation, and anything else you'd like to call out or ask reviewers. Explain how the changes were verified.

The easiest way to test this is:

1. Checkout the PR locally
2. Run npm build && npm link
3. In a separate directory (empty) run npm link @common-grants/cli
4. Create a test directory and change directory into it: mkdir test-default && cd test-default
5. Run cg init --list
6. Run cg init --template default-api and complete the interactive setup

Additional information

Screenshots, GIF demos, code examples or output to help show the changes working as expected.