doc/upsert: add example for clearing and de/incrementing fields (#1994)

doc/md/crud.md

@@ -231,6 +231,8 @@ err := client.User.
 	// Override some of the fields with a custom update.
 	Update(func(u *ent.UserUpsert) {
 		u.SetAddress("localhost")
+		u.AddCount(1)
+		u.ClearPhone()
 	}).
 	Exec(ctx)
 ```

doc/website/src/css/custom.css

@@ -566,7 +566,7 @@ header ul, ol {
 
 @media only screen and (min-width: 1425px) {
   .homeContainer {
-    padding: 0 19% 20px;
+    padding: 0 19% 50px;
   }
 
   .home-nav {