README.md: Note about impulse 255 command (#714)

[skip ci]

Author: UnkwUsr

README.md

@@ -28,6 +28,7 @@ This means that plugins that do binary code analysis (Orpheu for example) probab
 | endround                            | Args:<br/>`T` force round end with Terrorists win. <br/>`CT` force round end with Counter-Terrorists win. <br/> or terminate round draw when called without arguments. |
 | swapteams                           | Swap the teams and restart the game. |
 | give                                | Give weapon command.<br/> Args:<br/><weapon_name><br/>Usage:<br/>`give weapon_ak47`<br/>`give weapon_usp`<br/><br/>NOTE: `sv_cheats 1` required. |
+| impulse 255                         | Give all weapons.<br/><br/>NOTE: `sv_cheats 1` required. |
 
 ## Configuration (cvars)
 <details>