use egl config with alpha channel

Author: Brazol

android/src/main/java/io/getstream/webrtc/flutter/SurfaceTextureRenderer.java

@@ -40,8 +40,8 @@ public SurfaceTextureRenderer(String name) {
   }
 
   public void init(final EglBase.Context sharedContext,
-                   RendererCommon.RendererEvents rendererEvents) {
-    init(sharedContext, rendererEvents, EglBase.CONFIG_PLAIN, new GlRectDrawer());
+      RendererCommon.RendererEvents rendererEvents) {
+    init(sharedContext, rendererEvents, EglBase.CONFIG_RGBA, new GlRectDrawer());
   }
 
   /**

android/src/main/java/io/getstream/webrtc/flutter/utils/EglUtils.java

@@ -19,9 +19,9 @@ public class EglUtils {
     public static synchronized EglBase getRootEglBase() {
         if (rootEglBase == null) {
             if (Build.VERSION.SDK_INT < Build.VERSION_CODES.LOLLIPOP)
-                rootEglBase = EglBase.createEgl10(EglBase.CONFIG_PLAIN);
+                rootEglBase = EglBase.createEgl10(EglBase.CONFIG_RGBA);
             else
-                rootEglBase = EglBase.create();
+                rootEglBase = EglBase.create(null, EglBase.CONFIG_RGBA);
         }
 
         return rootEglBase;