HTTPS Everywhere in EASE mode blocks redirect to http://*.localhost

There is an Encrypt All Sites Eligible (EASE) opt-in mode in [HTTPS Everywhere](https://github.com/EFForg/https-everywhere/) which protects users against downgrade from `https://` to `http://` even when HSTS header is not present.

## Problem

This is a minor inconvenience for DNSLink redirects to `*.localhost` subdomains introduced in #853, as those get blocked if the feature is enabled:

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## Solution

- Before starting work, check if the issue is limited to Firefox
- if so, this may go away when Firefox marks `*.localhost` as Secure Context ([Bug 1220810](https://bugzilla.mozilla.org/show_bug.cgi?id=1220810#c23)), but that depends on how HTTPS Everywhere determines "unsafe" redirect (won't help if they just look at URL.protocol scheme, and not if URL.origin is Secure Context)
- Universal fix: PR HTTPS Everywhere to exclude redirects to `*.localhost` as browser vendors hardcode it to point at loopback IP and mark it as Secure Context