v2.1

New features:

• Upside-down printing is now implemented #615
• Include updates from escpos-printer-db

Bug and code fixes:

• Modify validation code in WindowsPrintConnector for PHP 7.3 compatibility
• Add to type hints where possible, replace old usages in examples, and correctly label the namespace for some exceptions

Newly tested printers:

• OKI RT322
• ithaca ITherm 280
• Rongta RP80USE
• Sewoo SLK-TS400
• Approx APPPOS80AM
• QPOS Q58M
• HOIN HOP-H58
• Xeumior SM-8330
• Birch PRP-085III
• 3nStar RPT-008
• POSLIGNE ODP200H-III-G