Fix Firefox CSP upgrading ws:// to wss:// for local WebSocket connections

Firefox's default MV3 CSP includes upgrade-insecure-requests, which upgrades
ws://127.0.0.1 to wss:// and breaks SSH/RDP WebSocket connections to the
local native host. Add explicit content_security_policy to manifest_firefox.json
allowing ws://127.0.0.1:* and http://127.0.0.1:* on extension pages.

extension/manifest_firefox.json

@@ -89,6 +89,9 @@
       "strict_min_version": "109.0"
     }
   },
+  "content_security_policy": {
+    "extension_pages": "default-src 'self'; script-src 'self'; connect-src 'self' ws://127.0.0.1:* http://127.0.0.1:*;"
+  },
   "host_permissions": [
     "*://*.host.local/*",
     "*://*.hole.sail/*"