Improve typing useCKEditorCloud to make it more narrow

[Mati365]

Suggested merge commit message (convention)

Feature: Improve result type of useCKEditorCloud to make CKEditorPremiumFeatures and CKBox non-nullable when proper configuration is passed.
Fix: Rename the languages configuration property to translations in useCKEditorCloud.

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Additional information

Must be released before testing:
ckeditor/ckeditor5-integrations-common#25

PRs family:
ckeditor/ckeditor5-react#523

const { CKEditorPremiumFeatures } = await loadCKEditorCloud( {
  version: '43.0.0',
  premium: true,
  ckbox: {
    version: '2.5.1'
  }
} );

Before:

CKEditorPremiumFeatures is nullable type.

After:

CKEditorPremiumFeatures is not nullable type because premium: true is passed.

[coveralls]

Pull Request Test Coverage Report for Build f15cc5e5-5eaa-449e-9fb0-f8c01d365edd

Details

• 1 of 1 (100.0%) changed or added relevant line in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 100.0%

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Totals
Change from base Build a9ce65d7-d9ba-471c-ae1d-3feea36e2f99:	0.0%
Covered Lines:	79
Relevant Lines:	79

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💛 - Coveralls