xdph: add config section

pages/Hypr Ecosystem/xdg-desktop-portal-hyprland.md

@@ -8,7 +8,20 @@ allows for screensharing, global shortcuts, etc.
 
 ## Configuration
 
-No configuration.
+Example:
+```ini
+screencopy {
+    max_fps = 60
+}
+```
+
+Config file `~/.config/hypr/xdph.conf` allows for these variables:
+
+### category screencopy
+
+| variable | description | type | default value |
+| -- | -- | -- | -- |
+| max_fps | Maximum fps of a screensharing session. 0 means no limit. | int | 120 |
 
 ## Troubleshooting