parse ion mobility (IM) from idxml to PSM obj

Author: jonasscheid

psm_utils/io/idxml.py

@@ -187,7 +187,7 @@ def _parse_psm(
             score=peptide_hit.getScore(),
             precursor_mz=peptide_id.getMZ(),
             retention_time=peptide_id.getRT(),
-            # NOTE: ion mobility will be supported by OpenMS in the future
+            ion_mobility=float(peptide_id.getMetaValue("IM")) if peptide_id.getMetaValue("IM") is not None else None
             protein_list=[
                 accession.decode() for accession in peptide_hit.extractProteinAccessionsSet()
             ],