Support Typescript with @intlify/vue-i18n/no-missing-keys

[maggie44]

What rule do you want to change?
@intlify/vue-i18n/no-missing-keys

Does this change cause the rule to produce more or fewer warnings?
It would produce warnings that the user would expect to be produced when working in Typescript (.ts files).

How will the change be implemented? (New option, new default behavior, etc.)?
Mirror the procedure used for @intlify/vue-i18n/no-unused-keys:

Example (not currently supported):

    '@intlify/vue-i18n/no-missing-keys': [
      'error',
      {
        src: './src',
        extensions: ['.js', '.vue', '.ts'],
        ignores: []
      }
    ],

Alternatively, just check .ts files by default.

What does the rule currently do for this code?
It currently doesn't apply to files ending in .ts.

Additional context
This pattern can be seen by putting in a console.log(t('any_key')) in to a .ts file, a .vue file and a .js file. The rule only works for the .vue and .js files.