Add SCREAMING_SNAKE_CASE to key-format-style rule

[nolde]

What rule do you want to change?
@intlify/vue-i18n/key-format-style

Does this change cause the rule to produce more or fewer warnings?
Depends.

How will the change be implemented? (New option, new default behavior, etc.)?
New option, slightly changed behaviour (snake_case would stop matching SCREAMING_SNAKE_CASE).

Please provide some example code that this change will affect:
Allow SCREAMING_SNAKE_CASE as an allowed option.

<i18n>
{
  "en": {
    "states": {
      "RUNNING": "Your process is still running.",
      "COMPLETED": "The process has been completed successfully.",
      "FAILED": "The process has failed."
    }
  }
}
</i18n>

What does the rule currently do for this code?
There is no option that differentiates SCREAMING_SNAKE_CASE from common snake_case right now.

What will the rule do after it's changed?
SCREAMING_SNAKE_CASE naming pattern is pretty common for enumerations and other similar constants in JavaScript. By making it different from normal snake_case and allowing independent setting, this pattern can be supported.

Additional context
Google's JavaScript naming conventions