Require jQuery UI Draggable

composer.json

@@ -110,7 +110,8 @@
         "npm-asset/select2": "^4.0.7",
         "caxy/php-htmldiff": "^0.1.14",
         "webonyx/graphql-php": "^14.11.8",
-        "drupal/jquery_ui": "^1.6"
+        "drupal/jquery_ui": "^1.6",
+        "drupal/jquery_ui_draggable": "^2.1"
     },
     "suggest": {
         "drupal/search_api_solr": "Provides a Apache Solr backend for the Search API module"

docs/developer-guide/migration/migrate-7-8.md

@@ -0,0 +1,39 @@
+# Update Thunder 7 -> Thunder 8
+
+## Prerequisites
+
+These are the instructions to manually update your existing Thunder 7 installation to Thunder 8. If
+you want to do a fresh installation of thunder please visit [install Thunder](../setup.md#install-thunder).
+
+You have to make sure that your Thunder 7 project and all its dependencies are fully updated to the most current
+versions. Run the following command in your docroot:
+
+```bash
+drush ev "print drupal_get_installed_schema_version('thunder') . PHP_EOL;"
+```
+
+This should print the number XXXX or greater. If that is not the case, update your project.
+
+```bash
+cd ..
+composer update
+```
+
+This should update to Thunder 7.3 or greater.
+
+Now run database updates:
+
+```bash
+cd docroot
+drush updb
+```
+
+You should at least see the Thunder XXXX schema update. If not, double check that the correct version of Thunder
+is installed, and that `drush updb` did not throw any errors.
+
+Before you start with the code and database update please disable the jQuery UI Draggable module or require it on your own.
+
+```bash
+composer require drupal/jquery_ui_draggable
+```
+