Mention that grab_focus is more reliable deferred

doc/classes/Callable.xml

@@ -75,6 +75,10 @@
 			<return type="void" />
 			<description>
 				Calls the method represented by this [Callable] in deferred mode, i.e. during the idle frame. Arguments can be passed and should match the method's signature.
+				[codeblock]
+				func _ready():
+				    grab_focus.call_deferred()
+				[/codeblock]
 			</description>
 		</method>
 		<method name="get_method" qualifiers="const">

doc/classes/Control.xml

@@ -553,6 +553,7 @@
 			<return type="void" />
 			<description>
 				Steal the focus from another control and become the focused control (see [member focus_mode]).
+				[b]Note[/b]: Using this method together with [method Callable.call_deferred] makes it more reliable, especially when called inside [method Node._ready].
 			</description>
 		</method>
 		<method name="has_focus" qualifiers="const">