New option to use and configure Prosody mod_firewall WIP (#97):

* new setting
* new configuration screen for Peertube admins
* include the mod_firewall module
* load mod_firewall if enabled
* sys admin can disable the firewall config editing by creating a
  special file on the disk
* user documentation

client/admin-plugin-client-plugin.ts

@@ -270,6 +270,8 @@ function register (clientOptions: RegisterClientOptions): void {
           return !(options.formValues['chat-all-lives'] === true && options.formValues['chat-per-live-video'] === true)
         case 'auto-ban-anonymous-ip':
           return options.formValues['chat-no-anonymous'] !== false
+        case 'prosody-firewall-configure-button':
+          return options.formValues['prosody-firewall-enabled'] !== true
       }
 
       if (name?.startsWith('external-auth-')) {