Automatically use Nextcloud translated months, days and years

[skjnldsv]

First step towards properly defined translations.

The only thing missing is translating nice strings in the input, for that we need to use the formatter prop with moment, so far this can be done in the app directly:

https://github.com/mengxiong10/vue2-datepicker/tree/v3.10.0#formatter

formatter: {
    stringify: (date) => {
        return date ? moment(date).format('LL') : ''
    },
},

Supersede: #146