Update Bidi and Font Features demo for 4.0.rc4

- Enable low processor mode and multiple resolution-friendly
  project settings for consistency with other demos.
- Use Compatibility rendering method for better performance
  and compatibility.
- Prevent screenshots from being imported as resources.

gui/bidi_and_font_features/README.md

@@ -1,13 +1,15 @@
-BiDI and Font Features Demo
+# BiDI and Font Features Demo
 
 A demo showing BiDi text and BiDi overrides, line breaking and justification, and OpenType font features.
 
 Language: GDScript
 
-Renderer: Vulkan
+Renderer: Compatibility
 
 ## Screenshots
 
 ![Screenshot](screenshots/bidi.png)
+
 ![Screenshot](screenshots/line_break_and_fill.png)
+
 ![Screenshot](screenshots/font_features.png)