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

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

@@ -31,7 +31,7 @@ import lombok.extern.slf4j.Slf4j;
  * enables an algorithm's behavior to be selected at runtime.</p>
  *
  * <p>Before Java 8 the Strategies needed to be separate classes forcing the developer
- * to write lots of boilerplate code. With modern Java it is easy to pass behavior
+ * to write lots of boilerplate code. With modern Java, it is easy to pass behavior
  * with method references and lambdas making the code shorter and more readable.</p>
  *
  * <p>In this example ({@link DragonSlayingStrategy}) encapsulates an algorithm. The containing