feat: use system theme by default (#932)

* feat: use system theme by default

* Move logic to default prop

Co-authored-by: Steve Ruiz <steveruizok@gmail.com>

packages/tldraw/src/Tldraw.tsx

@@ -102,6 +102,10 @@ export interface TldrawProps extends TDCallbacks {
   disableAssets?: boolean
 }
 
+const isSystemDarkMode = window.matchMedia
+  ? window.matchMedia('(prefers-color-scheme: dark)').matches
+  : false
+
 export function Tldraw({
   id,
   document,
@@ -116,7 +120,7 @@ export function Tldraw({
   showUI = true,
   readOnly = false,
   disableAssets = false,
-  darkMode = false,
+  darkMode = isSystemDarkMode,
   onMount,
   onChange,
   onChangePresence,