Add the option to upload a document to the Organisation Data document-link element

[emmajclegg]

The document "Upload" button is currently available for the activity level document-link element, but not elsewhere in IATI Publisher.

Can we add the same upload option for the Organisation Data document-link element (this is the most popular other area to require documents). After conversations with the Dutch MFA, we know that document links are not encouraged at either transaction or results level.

[emmajclegg]

@praweshsth - I'm deprioritising this task in the backlog of proposed tasks, as I think #1542 and #1480 are higher value to users in the short term. So if there is spare developer capacity this month (September), those are the two tasks to look at.

Obviously bugs like #1501 take top priority.