[thumbnails] change background-size default value

[axel7083]

The chonky-fileThumbnail class has the css value background-size set to contain, in some case we might want to have this value set to cover to take the full space available.

However, setting the following css

.chonky-fileThumbnail {
    background-size: cover;
}

Does not seems to work even, when importing after the chunky css.

[axel7083]

The current work around is to use the following css synthax:

.chonky-fileThumbnail {
    background-size: cover !important;
}