Add keyboard shortcut for saving annotations with Ctrl+S

index.html

@@ -664,6 +664,11 @@ function showToast(msg, type) {
 }
 
 document.addEventListener("keydown", e => {
+  if ((e.ctrlKey || e.metaKey) && e.key.toLowerCase() === "s") {
+    e.preventDefault();
+    if (!document.getElementById("btn-save").disabled) saveAnnotation();
+    return;
+  }
   if (e.target.tagName === "SELECT" || e.target.tagName === "TEXTAREA") return;
   if (e.key === "ArrowLeft")  navigate(-1);
   if (e.key === "ArrowRight") navigate(1);