QOL improvements and fixes to reported bugs

I never thought we would get so many contributions 🥲

We have a fix to a critical bug that was bothering some users for some time, as described in #72

• Fix UWPHook 'deleting' custom grid artwork added by other apps

And thanks to the contributions of @EnumC, we have a few features

• The app will no longer create duplicated entries, will update existing shortcuts if trying to export an identical app

• Properly handle error responses from SteamGridDB and display a nice message before exiting

• Properly fit the SteamGridDB key in the settings page

• (Only for devs/contributions) A debug option to clean shortcuts during development

  When UWPHook as re-serializing pre-existing shortcuts, it changed some properties read by Steam, changing the value of the appid Steam uses to track the link between games and the custom grid artwork, this update will no longer tamper with these shortcuts and will keep your library tidy and clean 😄
  Also, since some people reported that some anti-viruses are mistakenly reporting the attached zip as "malware", i'll be naming the zipped version of releases as UWPHook.zip from now on, since Release.zip seems to be used by some malwares, causing this false-positive.

If you face bugs or have questions, head over to our subreddit at http://reddit.com/r/UWPHook or ping me at our issues or my Twitter.

This software is open-source under the MIT License.

If you like what i did with it and want to support me, you can cheer me up at my Twitter or pay me a coffee via Paypal, it will help me to continue to build amazing open source tools for you!

Thanks for your support, and game on!