Added Dart 3.0 compatibilty, implemented custom translations

[FredrikBorgstrom]

If a translation by Google is incorrect or less suitable, you can override it by adding an 'x-translations' attribute and then specify your own translation for any specified language code. For instance, overriding the Swedish translation of the word "Continue" to "Fortsätt" would be done like this:

"continue_": "Continue",
"@continue_": {
  "description": "custom translations",
  "x-translations": {
    "sv": "Fortsätt"
  }
}

[justkawal]

Github Actions failing, I think its a dependency issue....