task: Explanations and grammar fixes for all the GoF patterns (#1791)

* Grammatical fixes to command pattern

* Update bridge pattern readme

* Fixes to builder pattern grammar

* Update chain of responsibility

* Improvements to the composite example

* Fixes to headings

* Minor updates to decorator pattern

* Update facade

* Update factory example

* Update factory method

* Update flyweight

* Interpreter explanation

* Update iterator readme

* Add explanation for mediator pattern

* Grammatical fixes to memento

* Grammar fixes for observer

* Update explanation for the prototype pattern

* Proxy pattern grammar fixes

* Update singleton

* Grammar fixes to state pattern

* Grammar fixes for strategy

* Grammar fixes, template method

* Grammar fixes for visitor

* Fix typo

state/src/main/java/com/iluwatar/state/App.java

@@ -24,7 +24,7 @@
 package com.iluwatar.state;
 
 /**
- * In State pattern the container object has an internal state object that defines the current
+ * In the State pattern, the container object has an internal state object that defines the current
  * behavior. The state object can be changed to alter the behavior.
  *
  * <p>This can be a cleaner way for an object to change its behavior at runtime without resorting

state/src/main/java/com/iluwatar/state/State.java

@@ -31,5 +31,4 @@ public interface State {
   void onEnterState();
 
   void observe();
-
 }