structural/proxy: implement structural proxy pattern (#27)

* Update gitignore added JetBrains, LiteIDE and other exclude files

* Added example of proxy realisation

* Update proxy description with simple example

* Update showcase with description, small refactore of code

* Update proxy doc

* Added comments in example proxy also added link to go play sandbox

* Small improvement of proxy example

* Update link for play golang

* Corrected mistakes, splited user validation in proxy

* Updated link to play golang and some mistakes

README.md

@@ -30,7 +30,7 @@ A curated collection of idiomatic design & application patterns for Go language.
 | [Decorator](/structural/decorator.md) | Adds behavior to an object, statically or dynamically | ✔ |
 | [Facade](/structural/facade.md) | Uses one type as an API to a number of others | ✘ |
 | [Flyweight](/structural/flyweight.md) | Reuses existing instances of objects with similar/identical state to minimize resource usage | ✘ |
-| [Proxy](/structural/proxy.md) | Provides a surrogate for an object to control it's actions | ✘ |
+| [Proxy](/structural/proxy.md) | Provides a surrogate for an object to control it's actions | ✔ |
 
 ## Behavioral Patterns