Almost 30% of the entries are useless

I created a python script which uses the information available and checks the provided urls and I found out that almost 30% of the packages

- do not have any download url (around 256 packages)
- download url returns 404 (around 31)
- does not offer an AppImage in the releases because they stopped offering one (around 129)

here the script (rename from txt to py, GitHub does not accept .py files):

[Appchecker.txt](https://github.com/AppImage/appimage.github.io/files/8766335/Appchecker.txt)

and here my results including the list of applications in each category:

[results.txt](https://github.com/AppImage/appimage.github.io/files/8766338/results.txt)

I think it would be good to clean this up a bit, because otherwise this repository will become more and more useless and frustrating for users.