Add --init-emojis option to suggest emojis for configs

[bmish]

This new option --init-emojis uses gpt-emoji (which queries OpenAI for a suggestion on what emoji to use to represent the given text) to suggest an emoji to represent each of the user's configs.

For example, with a config name statements, the AI may suggest "🗣️" as the emoji to represent it.

This is useful especially when a user has one or more obscure config names, and needs to pick a unique emoji to represent each for good documentation understandability and aesthetics.

Related: #394

TODO:

• Output the suggestions with table
• Add tests
• Document OPENAI_API_KEY requirement
• Throw an exception if OPENAI_API_KEY environment variable missing
• Avoid suggesting the same emoji for multiple configs
  • Add option to ignore certain emoji(s) in suggestions gpt-emoji#1
  • Add bulk API to query for several results at once gpt-emoji#3
• Provide multiple, single-emoji suggestions for each config?

Sample output with eslint-plugin-import:

eslint-doc-generator --init-emojis
╔══════════════╤═══════╗
║ Config       │ Emoji ║
╟──────────────┼───────╢
║ recommended  │ 👍    ║
╟──────────────┼───────╢
║ errors       │ ❗️   ║
╟──────────────┼───────╢
║ warnings     │ ⚠️    ║
╟──────────────┼───────╢
║ stage-0      │ 0️    ║
╟──────────────┼───────╢
║ react        │ ⚛️    ║
╟──────────────┼───────╢
║ react-native │ 📱    ║
╟──────────────┼───────╢
║ electron     │ 💻    ║
╟──────────────┼───────╢
║ typescript   │ 🆕️   ║
╚══════════════╧═══════╝