firewalld: Add polkit JS authority rules files

This should help with FreedomBox getting authorizations to access firewalld
D-Bus API for polkit versions > 0.105 where polkit local authority is not
available.

Helps #1728.

Tests performed:

- Install policykit-1 version 0.105. Something like apt install
policykit-1=0.105-26 libpolkit-agent-1-0=0.105-26 libpolkit-gobject-1-0=0.105-26

  - Visit privoxy page. See internal networks warning with all the interfaces
  listed properly.

  - Visit firewalld page, view list of apps and services properly.

  - Enable privoxy, see the port opened in firewalld page.

  - Disable privoxy, see the port closed in firewalld page.

  - Run diagnostics for privoxy see that ports' diagnostics results pass.

- Add Debian experimental to /etc/apt/sources.list. apt update. Then install
policykit-1 version 0.116. apt install -t experimental policykit-1.

  - Repeat all above tests.

Signed-off-by: Sunil Mohan Adapa <sunil@medhas.org>
Reviewed-by: Veiko Aasa <veiko17@disroot.org>

plinth/modules/firewall/data/usr/share/polkit-1/rules.d/50-freedombox-firewalld.rules

@@ -0,0 +1,16 @@
+/*
+# SPDX-License-Identifier: AGPL-3.0-or-later
+
+This file is used only by policykit-1 version > 0.105. A corresponding .pkla
+file is used by policykit-1 <= 0.105. See:
+https://davidz25.blogspot.com/2012/06/authorization-rules-in-polkit.html
+
+*/
+
+polkit.addRule(function(action, subject) {
+    if ((action.id == "org.fedoraproject.FirewallD1.config.info" ||
+         action.id == "org.fedoraproject.FirewallD1.config") &&
+        subject.user == "plinth") {
+        return polkit.Result.YES;
+    }
+});