• [plistlib] Added typing annotations to plistlib module. Set up mypy static typechecker to run automatically on CI (#2061).
• [ttLib] Implement private Debg table, a reverse-DNS namespaced JSON dict.
• [feaLib] Optionally add an entry into the Debg table with the original lookup name (if any), feature name / script / language combination (if any), and original source filename and line location.
  Annotate the ttx output for a lookup with the information from the Debg table (#2052).
• [sfnt] Disabled checksum checking by default in SFNTReader (#2058).
• [Docs] Document mtiLib module (#2027).
• [varLib.interpolatable] Added checks for contour node count and operation type of each node (#2054).
• [ttLib] Added API to register custom table packer/unpacker classes (#2055).