Add white background to drawings for improved dark mode readability (#9475)

docs/resources/firebase_from_dynamic_framework.svg

@@ -50,6 +50,7 @@
      inkscape:document-rotation="0"
      bordercolor="#666666"
      pagecolor="#ffffff" />
+  <rect width="100%" height="100%" fill="white" />
   <clipPath
      id="p.0">
     <path

docs/resources/firebase_from_static_framework.svg

@@ -50,6 +50,7 @@
      inkscape:document-rotation="0"
      bordercolor="#666666"
      pagecolor="#ffffff" />
+  <rect width="100%" height="100%" fill="white" />
   <clipPath
      id="p.0">
     <path