Adds example on how to safely escape params for XML

[gradha]

Through the addition of a simple conditional selector the code can be used to safely escape XML/HTML parameters automatically. This would be useful for all the cases when you have to build a string but it's not big enough that you want to import a full-fledged XML parsing/building library to create a proper XML tree and build a string from it.

This may not be production code, but still can be useful.