Support entry of many IGSNs

[nuest]

From the conversation with the IGSN team, I found an old note that they consider the option to provide many (hundreds) IGSNs in bulk, for example by copying a column from a spreadsheet and pasting it into a multiline text field in OJS.

[hauschke]

In the frontend this could be done by either displaying only a few IGSN at first and a "show more" button, or by implementing a search function.

Related issue: #13 - Add CSV download for IGSN

[hauschke]

Suggestion by Rorie:

Adding IGSN IDs through a batch upload (CSV) might be a solution.

Or a text field which is then parsed for DOIs. Might require a scheduled harvesting task according to @GaziYucel