improving elabFTW parser

• documentation of how to use the .ELN parser
• parse Markdown body field
• import elabFTW extra fields as interactive ELN fields in NOMAD
• linking to other elabFTW entries if also uploaded into NOMAD
• checkbox upload all attached files yes/no
• include .ELN files in overarching experimental structure schema (still needs to be developed)

The main issue lives in github repo here