v1.3.0

• Added item price base quantity (BT-149/BT-150). New optional
  basisQuantity and basisQuantityUnitCode fields on InvoiceLineInput
  emit ram:BasisQuantity inside the net (and, when present, gross) price
  element, so a unit price can state the quantity it refers to — e.g.
  12.50 per 10 m². The unit code defaults to the line's unitCode, as
  EN 16931 requires BT-150 to match BT-130. Omitting the field keeps the
  output byte-for-byte identical (#12).
• CI now requires every PR to add a CHANGELOG.md entry (or carry the
  skip-changelog label), so contributor fixes always reach the release notes.