Added custom text support for text uploading.
Example:

<html>
<body style="background-color:#333333">
<pre class="prettyprint">
%input
</pre>
<script src="https://google-code-prettify.googlecode.com/svn/loader/run_prettify.js?skin=desert"></script>
</body>
</html>

Will add syntax highlighting to uploaded text.
Merge branch 'master' of github.com:ShareX/ShareX