add entity:require_component

doc/en/scripting/ecs.md

@@ -26,6 +26,8 @@ entity:get_uid() -> int
 entity:get_component(name: str) -> component or nil
 -- Checks for the presence of a component by name
 entity:has_component(name: str) -> bool
+-- Retrieves a component by name. Throws an exception if it does not exist
+entity:require_component(name: str) -> component
 
 -- Enables/disables the component
 entity:set_enabled(name: str, enable: bool)