[util] Set maxChunkSize to 1 for Battle.net

Currently when Diablo 4 is running the Battle.net launcher it uses around
600MB of VRAM. Reducing the max chunk size to 1MB reduces the memory usage
to around 150MB.

src/util/config/config.cpp

@@ -387,6 +387,10 @@ namespace dxvk {
     { R"(\\Fallout76\.exe$)", {{
       { "dxgi.syncInterval",              "1" },
     }} },
+    /* Blizzard Entertainment Battle.net          */
+    { R"(\\Battle.net\.exe$)", {{
+      { "dxvk.maxChunkSize",                "1"   },
+    }} },
 
     /**********************************************/
     /* D3D9 GAMES                                 */