[FEATURE] Proxy support

[chenxiex]

Is your feature request related to a problem? Please describe.
I'm behind a network that needs proxy to download from github. However, I don't find a proxy option in the app. I also tried setting environment variables like flatpak run --env=HTTP_PROXY="http://localhost:10808" --env=HTTPS_PROXY="http://localhost:10808" --env=ALL_PROXY="http://localhost:10808" com.vysp3r.ProtonPlus, but it doesn't work either.

Describe the solution you'd like
Add some setting options like "Proxy URL" in the app that can enable proxy.

Describe alternatives you've considered
Read the proxy option from the environment variables and use it.

Additional context
v0.5.15, Flatpak

[Vysp3r]

I'll check to see how to implement that since I have no clue how to do that right now.

[Vysp3r]

I've talked with a friend that knows more about that and he told me to ask you why you simply don't use the proxy on your system?

[chenxiex]

I've talked with a friend that knows more about that and he told me to ask you why you simply don't use the proxy on your system?

Here are several reasons. As far as I know, the "system proxy" is a DE-specific feature. Only some DEs have this feature, and they implement it differently. For example, Xfce doesn't have a proxy configuration option, and KDE implements proxies differently with Gnome. What's more, proxies are expensive and has bandwidth limitation, so I want to limit the usage.