Add related Shader stuff;

api/lovr/graphics/Shader/init.lua

@@ -91,5 +91,9 @@ return {
         model:draw(x, y, z, 1)
       end
     ]=]
+  },
+  related = {
+    'lovr.graphics.setShader',
+    'lovr.graphics.getShader'
   }
 }

api/lovr/graphics/newShader.lua

@@ -24,5 +24,9 @@ return {
       type = 'Shader',
       description = 'The new Shader.'
     }
+  },
+  related = {
+    'lovr.graphics.setShader',
+    'lovr.graphics.getShader'
   }
 }