Add support for custom annotations #3
Description
Example custom annotations from Eric on PeptideAtlas:
https://db.systemsbiology.net/dev2/sbeams/cgi/PeptideAtlas/ShowObservedSpectrum?atlas_build_id=442&spectrum_identification_id=1732242408&peptide=n%5b145%5dATAAGATYFQR&assumed_charge=2&SAWB_DisplayMode=Lorikeet