xnotes 0.8.15

• Save a large note in a fraction of the time, and never on the main thread
• Save a stroke into a PDF note without rewriting the whole PDF
• Open a big handwriting note several times faster
• Undo on a dense note repaints only what changed instead of hanging
• Fix ink blinking out when one stroke starts right after another
• Fix a crash closing a PDF note mid-render, and an out of memory on save
• Fix a canvas autosave silently dropping a write you drew during