store description, translation, Internationalization, localization

[ImprovedTube]

To Do:

1. We should internationalize:

• title (maximum 45 characters)
• short description (max. 132 chars)

works in the language files https://developer.chrome.com/webstore/i18n#manifest

2. • Long description for the chrome webstore: Basically just a nice introduction + feature-list ordered by popularity.
     (As the English one is not good nor updated, it need not all be translated). Any contribution can be added in an issue or file to the repository. We can still improve English first and generate draft feature-lists for languages from our existing language files)

     • Developer Info: Full description ("detailed description") can't be uploaded by webstore API yet ( https://developer.chrome.com/webstore/api_index#Items
       https://developer.chrome.com/webstore/using_webstore_api#usingtheapi )

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#1647
#543 (comment)
#623 (done)

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translating ImprovedTube