v3.4.0: Extended Latin as default character set

• After the Swiss Payment Standards 2025 have gone into effect in November 2025, the default character set used in the QR bills has been switched to Extended Latin so QR bills generated with the library support the full character set by default.
• The built-in PDF generator can now generate PDF files with an embedded font subset. This is required for the Extended Latin character set and active by default.