Updated ingest spreadsheet file source metadata

[ESapenaVentura]

As discussed in the demo meeting on Tues 6th, I have added the file_source content expected in the supplementary file associated with the Ingest Spreadsheets

[hannes-ucsc]

@ESapenaVentura, I added a commit that fixes grammar and formatting in the existing text, and another commit to convert the bullets to a preformatted JSON fragment. Technically, I shouldn't push to other people's branches, so feel free to remove them.

@ncalvanese1, I should also have asked for a re-review but given that the commits don't alter the semantics, I wanted to save you time.

[MightyAx]

I've updated the example used to make it explicit that content_description is an array. Because we are using supplementary_file 2.5 which references file_core 6.4, which states that: content_description is an array of file_content_ontology 1.1 objects.