Improve translations tooling to include fully translated languages

[sarathms]

This is about how we fetch new strings from transifex and bundle them in our apps. The objective is to look at the translation status of each language and use only those which have reached a ${threshold}% of completion.

We should look into using the Transifex API for statistics for this:

$ curl -i -L --user api:<token> -X GET https://www.transifex.com/api/2/project/transifex/resource/core/stats/
...
        "untranslated_entities": 1220
    }, 
    "pl": {
        "proofread": 0, 
        "proofread_percentage": "0%", 
        "reviewed_percentage": "0%", 
        "completed": "95%", 
        "untranslated_words": 3687, 
        "last_commiter": "transifex", 
        "reviewed": 0, 
        "translated_entities": 4025, 
        "translated_words": 26705, 
        "last_update": "2020-04-16 07:50:41", 
        "untranslated_entities": 207
    }, 
    "uk": {
        "proofread": 39, 
        "proofread_percentage": "0%", 
        "reviewed_percentage": "0%", 
        "completed": "92%", 
        "untranslated_words": 3867, 
        "last_commiter": "transifex", 
        "reviewed": 39, 
        "translated_entities": 3934, 
        "translated_words": 26525, 
        "last_update": "2020-04-16 07:50:41", 
        "untranslated_entities": 298
    }, 
    "sc": {
        "proofread": 0,