Domain Socks Proxy Helper per nshaaban-cpacket

Allows configuration of multiple socks proxies per domain.

Note: in order to populate DNS over socks:
- The global proxy setting is briefly set to each of your proxies on startup. Some of your requests when the browser is first starting may go through the socks proxy.
- Must have permission to run in private in order to set global proxy settings (See note on https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/API/proxy/settings for why)

Fork of https://addons.mozilla.org/en-US/firefox/addon/containers-proxy-helper/ but modified to per-domain rather than per-container.