feat: add socks5 proxy server

[angelakis]

Description

I would like to add simple socks5 functionality. I know shadowsocks exists already but not all tools can use it. It's a long requested feature.

I am not a Go developer and I implemented this by adding a new dependency that maybe is not the preferred way considering you have implemented an ss-server to use here for shadowsocks. The dependency I added is ancient but seems stable enough and with no obvious (to me) flaws. I can change it to something else if needed. But anyways, as I implemented the feature and I am actively using it, I thought of creating a PR.

If it's going to be accepted I can create a PR for the wiki also.

Issue

#234

Assertions

• I am aware that we do not accept manual changes to the servers.json file
• I am aware that any changes to settings should be reflected in the wiki

[qdm12]

Hi @angelakis thanks for the contribution!
I appreciate the work, unfortunately (my bad for the bad communication):

• as you guessed correctly I'm aiming at less dependencies (kind of ruined with protonvpn servers update authentication but oh well - i think i will change that soon)
• i already have a (wip) socks5 branch 😄 re-inventing the wheel I suppose, but at least it's minimal and only-server-code, no external dependency. However it's lacking the newer loop code you've put so I will just hijack your branch, merge in the socks5 branch in yours so you get some credits for the grunt work done! I will re-check my socks5 implementation is done and works find, it has been a few years since I wrote this and forgot about it 🫨

Note to self:

• update readme, labels, wiki
• document new options in pr