Add the list of available rails timezones to the base endpoint

[skateman]

There's no way to retrieve the list of available timezones from the frontend in a Rails-compatible way, so I'm adjusting the /api endpoint to provide a list of these.

# GET /api

{
  "name": "API",
  "description": "REST API",
  ...
  "timezones": [
    {
      "name": "International Date Line West",
      "description": "(GMT-12:00) International Date Line West"
    },
    {
      "name": "American Samoa",
      "description": "(GMT-11:00) American Samoa"
    },
    ...
  ],
  ...
}

[Fryguy]

I don't think we should expose a proper endpoint for something that isn't the domain of our application (imagine, for example, github exposed a /api/timezones endpoint, but it was because of some quirk of their UI...it just doesn't make sense).

Instead, can we just expose this from /api or OPTIONS /api ? I imagine this is a one-time thing that needs to be queried and cached by the UI.

[skateman]

@Fryguy updated

[miq-bot]

Checked commit skateman@e851c4d with ruby 2.6.3, rubocop 0.82.0, haml-lint 0.35.0, and yamllint
1 file checked, 0 offenses detected
Everything looks fine. 🏆

[Fryguy]

@gtanzillo Please also review.