Feature: Enable user selection of locale

[cedricium]

This is a small step in internationalizing amo-cli. These changes specifically allow the user to select their preferred locale, which is used in the lang query parameter when making GET requests aginst the AMO API. This is beneficial because the returned request will have add-on name, description, and other fields translated in the selected locale if supplied by add-on authors.

[cedricium]

TODOS:

• [x] error handling if locale cannot be read (fallback to en-US) - added: 00b6df5cd9a4673501db08b01dbaafa5f58be373
  • try...catch will be my friends :)
• [x] add cmd to allow changing locale - added: 0f76855d64cf0bc0cdf2f6d6ad6b4ea300d7db23
• [x] creation of config/default.json during postinstall 🤔 - added: ef34433c46745e82e7a3094859a1c37334ad2788
• [x] display info during (before and/or after) postinstall script describing why locale is necessary
  • basic info - added: 0f76855d64cf0bc0cdf2f6d6ad6b4ea300d7db23
  • next, add styling to output - added: e55a06c26e2adbdc087b377a19f6a72d931a0720