Add environment variable to enable/disable tours

NODE_RED_ENABLE_TOURS

Also had to patch editor-api/lib/editor/themes.js to pass
`editorTheme.tours` to the editor.

packages/node_modules/@node-red/editor-api/lib/editor/theme.js

@@ -228,6 +228,11 @@ module.exports = {
         if (theme.theme) {
             themeSettings.theme = theme.theme;
         }
+
+        if (theme.hasOwnProperty("tours")) {
+            themeSettings.tours = theme.tours;
+        }
+
         return themeApp;
     },
     context: async function() {