Create 15_HTMLTagReplacer.cs

15. Write a program that replaces in a HTML document given as string all the tags <a href="…">…</a> with corresponding tags [URL=…]…/URL].
Sample HTML fragment:

<p>Please visit <a href="http://academy.telerik. com">our site</a> to choose a training course. Also visit <a href="www.devbg.org">our forum</a> to discuss the courses.</p>

<p>Please visit [URL=http://academy.telerik. com]our site[/URL] to choose a training course. Also visit [URL=www.devbg.org]our forum[/URL] to discuss the courses.</p>