There are a number of apps and scripts for Windows that would allow you to manipulate plain text similar to that site. You would want to pick your poison and work from there. You could then assign that tool/script/whatever to a hotkey that would manipulate your clipboard text and paste.
If you want something on your desktop / not on the web:
Text Inspection & Manipulation Utility - small tool just for manipulating text, has UI but you can also use as command line utility so you could setup if you want same exact changes to the text every time. (like if you use that website with same exact options every time) - I think this would be closest to website you are using, and has more manipulation options. http://www.donationcoder.com/forum/index.php?topic=36544
Clipboard Help and Spell (Allows text manipulation) - easy to moderate - bigger program, more for saving text/images from your keyboard to allow you to easily access later (there are smaller clipboard history tools, but CHS allows creating automatic text manipulation. Allows you to change how you manipulate every time or save favorites. - http://www.donationcoder.com/Software/Mouser/clipboardhelpandspell/index.html
Autohotkey - Windows scripting language - advanced - though you might have found someone who already created AHK script or exe that does this https://www.autohotkey.com/