Proxy support

[Shamicen]

Closes #366

Implemented proxy support.

This is what the dialog looks like:

[AntsyLich]

I did some thinking and how likely is it that average user will use a proxy? This feature will probably be used by <0.01% of users. Most will probably install some free vpn and use that. Though the feature is simple to implement do we really want another option that will not be used by most of the user base?

[La-Hire]

I did some thinking and how likely is it that average user will use a proxy? This feature will probably be used by <0.01% of users. Most will probably install some free vpn and use that. Though the feature is simple to implement do we really want another option that will not be used by most of the user base?

Mainly because it's annoying work to add those domain rules in rule-based proxy app, and didn't want to use global proxy to affect some other apps (some app will ban account or mark account for ip change frequently). Especially some sources have several domains and cdn or change domain/redirect for some reason.

Of course, only few people need this function, may people just open global vpn when they read.

[AntsyLich]

Closing based on my rationale