Bump version to 1.1.0 and update README

Add accessibility section documenting WCAG 2.2 AAA compliance,
keyboard navigation, focus management, and theme support. Update
file handling with single-instance and OS association. Fix repo
URLs and version badge.

src-tauri/tauri.conf.json

@@ -1,7 +1,7 @@
 {
   "$schema": "https://schema.tauri.app/config/2",
   "productName": "Vesper",
-  "version": "1.0.1",
+  "version": "1.1.0",
   "identifier": "com.vesper.reader",
   "build": {
     "beforeDevCommand": "npm run dev",