Fix #192

[CalebQ42]

Fixes #192 by adding arguments that are present in the AppImage's desktop file to the generated desktop file. Also a partial fix for #183.

[CalebQ42]

Actually, should only field codes (such as %U) be included since other arguments should already be passed to the AppImage's AppRun by the AppImage itself? But then in #183 it's mentioned that --no-sandbox is needed in both places, which seems a bit odd.

[probonopd]

Thanks @CalebQ42.

But then in #183 it's mentioned that --no-sandbox is needed in both places, which seems a bit odd.

I think I can explain this, if memory serves me right:

So far, we have been disregarding arguments in desktop files in most places within the AppImage ecosystem. Instead, so far we have only used the first argument from the Exec= line and have appended any arguments given on the comand line to the AppImage. If I remember correctly.