Updated examples in commands.md (#323)

When I first looked at the documentation, I did not recognize that you can enter such values ​​in the <user> field. Thought I needed to clarify that this is possible.

docs/commands.md

@@ -133,6 +133,7 @@ ___
 
 * Example: `u:Notch`
 * Example: `u:Notch,Intelli`
+* Example: `u:#fire,#tnt,#creeper,#explosion`
 
 ---
 
@@ -276,4 +277,4 @@ Lookup commands are generally the same as rollback commands. The primary differe
 * `/co lookup u:Notch a:username`  
   *(lookup previous usernames used by Notch)*
 
-___
+___