Add Categories metadata field for each image

[RishikaBhatia17]

Users can select the category to which the image belongs to from a given list of categories in the drop down before they upload the image to Wikimedia commons as shown below.

[tonythomas01]

Good stuff. However, if we are to follow the way we do it on Commons ? This might be an extended task, as we might want the following:

1. Call https://commons.wikimedia.org/w/api.php?action=opensearch&format=json&formatversion=2&namespace=14&limit=10&search=Goog somehow, parase the result and populate a bubble input field. See example https://github.com/wikimedia/mediawiki-api-demos/blob/master/javascript/opensearch.js
2. A user can select more than one category on https://commons.wikimedia.org/wiki/Special:UploadWizard, we should support that. Since this is getting big, I think we should also have a phabricator task for it.

[RishikaBhatia17]

Thanks @tonythomas01 for the review. I will start working on this.