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

facade/README.md

@@ -17,7 +17,7 @@ interface that makes the subsystem easier to use.
 
 ## Explanation
 
-Real world example
+Real-world example
 
 > How does a goldmine work? "Well, the miners go down there and dig gold!" you say. That is what you 
 > believe because you are using a simple interface that goldmine provides on the outside, internally