Move the opdavies theme, add symlink

As per https://github.com/drupal-tome/tome-project.

> When composer install or update is ran, the "modules" and "themes"
directories, as well as the "settings.php" file, is symlinked into the
"web" directory.

composer.json

@@ -106,6 +106,13 @@
         "export": "drush tome:export --yes",
         "import": "drush tome:import",
         "generate": "drush tome:static --uri https://www.oliverdavies.uk",
+        "post-install-cmd": [
+            "@symlink"
+        ],
+        "post-update-cmd": [
+            "@symlink"
+        ],
+        "symlink": "./tools/scripts/symlink.sh",
         "test": [
             "composer validate --strict"
         ]