read_refs() failing to read in first field of first record

[nealhaddaway]

The first record isn't being read in properly - TY-JOUR is being shown in a 'ZZ' field instead of being recognised as source_type. I think this is because few RIS files have a field code signifying the start of the file, 'TY - ' is the start of the text file.

See this example from EMBASE: https://gitlab.com/extending-the-earcheck/living-review/-/blob/master/search/literature_search_02/Embase_290521_N974.RIS?expanded=true&viewer=simple

[shjenkins94]

Coming in late but I think the problem is that the file is UTF-8 with BOM. So there's some invisible characters before the first TY that cause a regexpr call in prep_ris to not match.