Removed transparent backgrounds to be viewable on GitHub dark mode.

doc/wrapping-upb.in.md

@@ -182,7 +182,6 @@ For example, a relatively simple protobuf tree might look something like this:
 digraph G {
   rankdir=LR; 
   newrank=true;
-  graph[bgcolor=transparent]
   node [style="rounded,filled" shape=box colorscheme=accent8 fillcolor=1, ordering=out]
   upb_msg -> upb_msg2;
   upb_msg -> upb_array;
@@ -201,7 +200,6 @@ from that arena are freed together.
 digraph G {
   rankdir=LR;
   newrank=true;
-  graph[bgcolor=transparent]
   subgraph cluster_0 {
     label = "upb Arena"
     graph[style="rounded,filled" fillcolor=gray]
@@ -227,7 +225,6 @@ the objects are in when you create links between them.
 digraph G {
   rankdir=LR;
   newrank=true;
-  graph[bgcolor=transparent]
   subgraph cluster_0 {
     label = "upb Arena 1"
     graph[style="rounded,filled" fillcolor=gray]
@@ -268,14 +265,13 @@ For this example, we will assume we are wrapping upb in Python:
 
 ```dot {align="center"}
 digraph G { 
-  graph[bgcolor=transparent]
   rankdir=LR;
   newrank=true;
   compound=true;
   
   subgraph cluster_1 {
     label = "upb Arena"
-    graph[bgcolor=transparent style="rounded,filled" fillcolor=gray]
+    graph[style="rounded,filled" fillcolor=gray]
     node [style="rounded,filled" shape=box colorscheme=accent8 fillcolor=1, ordering=out]
     upb_msg -> upb_array [style=dashed];
     upb_msg -> upb_msg2 [style=dashed];

doc/wrapping-upb/1.svg

@@ -8,6 +8,7 @@
  viewBox="0.00 0.00 222.00 98.00" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
 <g id="graph0" class="graph" transform="scale(1 1) rotate(0) translate(4 94)">
 <title>G</title>
+<polygon fill="white" stroke="transparent" points="-4,4 -4,-94 218,-94 218,4 -4,4"/>
 <!-- upb_msg -->
 <g id="node1" class="node">
 <title>upb_msg</title>

doc/wrapping-upb/2.svg

@@ -8,6 +8,7 @@
  viewBox="0.00 0.00 254.00 153.00" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
 <g id="graph0" class="graph" transform="scale(1 1) rotate(0) translate(4 149)">
 <title>G</title>
+<polygon fill="white" stroke="transparent" points="-4,4 -4,-149 250,-149 250,4 -4,4"/>
 <g id="clust1" class="cluster">
 <title>cluster_0</title>
 <path fill="gray" stroke="black" d="M20,-8C20,-8 226,-8 226,-8 232,-8 238,-14 238,-20 238,-20 238,-125 238,-125 238,-131 232,-137 226,-137 226,-137 20,-137 20,-137 14,-137 8,-131 8,-125 8,-125 8,-20 8,-20 8,-14 14,-8 20,-8"/>

doc/wrapping-upb/3.svg

@@ -8,6 +8,7 @@
  viewBox="0.00 0.00 409.00 153.00" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
 <g id="graph0" class="graph" transform="scale(1 1) rotate(0) translate(4 149)">
 <title>G</title>
+<polygon fill="white" stroke="transparent" points="-4,4 -4,-149 405,-149 405,4 -4,4"/>
 <g id="clust1" class="cluster">
 <title>cluster_0</title>
 <path fill="gray" stroke="black" d="M20,-8C20,-8 246,-8 246,-8 252,-8 258,-14 258,-20 258,-20 258,-125 258,-125 258,-131 252,-137 246,-137 246,-137 20,-137 20,-137 14,-137 8,-131 8,-125 8,-125 8,-20 8,-20 8,-14 14,-8 20,-8"/>

doc/wrapping-upb/4.svg

@@ -8,6 +8,7 @@
  viewBox="0.00 0.00 417.00 303.00" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
 <g id="graph0" class="graph" transform="scale(1 1) rotate(0) translate(4 299)">
 <title>G</title>
+<polygon fill="white" stroke="transparent" points="-4,4 -4,-299 413,-299 413,4 -4,4"/>
 <g id="clust1" class="cluster">
 <title>cluster_1</title>
 <path fill="gray" stroke="black" d="M29,-98C29,-98 380,-98 380,-98 386,-98 392,-104 392,-110 392,-110 392,-215 392,-215 392,-221 386,-227 380,-227 380,-227 29,-227 29,-227 23,-227 17,-221 17,-215 17,-215 17,-110 17,-110 17,-104 23,-98 29,-98"/>
@@ -15,11 +16,9 @@
 </g>
 <g id="clust2" class="cluster">
 <title>cluster_python</title>
-<polygon fill="transparent" stroke="transparent" points="8,-235 8,-287 401,-287 401,-235 8,-235"/>
 </g>
 <g id="clust6" class="cluster">
 <title>cluster_01</title>
-<polygon fill="transparent" stroke="transparent" points="8.5,-8 8.5,-90 239.5,-90 239.5,-8 8.5,-8"/>
 </g>
 <!-- upb_msg -->
 <g id="node1" class="node">