Adding a warning in settings if theme is not set to Peertube or if autocolors are disabled.

server/lib/settings.ts

@@ -532,7 +532,6 @@ function initThemingSettings ({ registerSetting }: RegisterServerOptions): void
     ] as Array<{ value: ConverseJSTheme, label: string }>,
     descriptionHTML: loc('converse_theme_description')
   })
-
   registerSetting({
     name: 'converse-autocolors',
     label: loc('autocolors_label'),
@@ -541,6 +540,12 @@ function initThemingSettings ({ registerSetting }: RegisterServerOptions): void
     private: false,
     descriptionHTML: loc('autocolors_description')
   })
+  registerSetting({
+    name: 'converse-theme-warning',
+    type: 'html',
+    private: true,
+    descriptionHTML: loc('converse_theme_warning_description')
+  })
 
   registerSetting({
     name: 'chat-style',