Add missing d32fs8 texture format;

api/lovr/data/TextureFormat.lua

@@ -89,6 +89,12 @@ return {
       name = 'd32f',
       description = 'One 32-bit floating point depth channel.  4 bytes per pixel.'
     },
+    {
+      name = 'd32fs8',
+      description = [[
+        One 32-bit floating point depth channel and one 8-bit stencil channel.  5 bytes per pixel.
+      ]]
+    },
     {
       name = 'bc1',
       description = [[