Proposal: move browser specific settings to `browser_specific_settings`

[carlosjeurissen]

Several manifest properties are browser specific like minimum_chrome_version and minimum_opera_version. To align with Safari, Firefox and edgeHTML, these should be defined in browser_specific_settings.

"browser_specific_settings": {
  "chromium": {
    "strict_min_version": "14",
    "strict_max_version": "20",
    "key": "some key",
    "container": "some container"
  },
  "opera": {
    "strict_min_version": "14",
    "strict_max_version": "20"
  }
}

Some of these can be specified as being the same for each platform. Like strict_min_version and strict_max_version, while some are unique for a specific platform like key and container are for Chromium.

[xeenon]

Safari already implements support for:

"browser_specific_settings": {
  "safari": {
    "strict_min_version": "14",
    "strict_max_version": "15",
  }
}

I believe Firefox does as well for the firefox key.