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.

tools/scripts/symlink.sh

@@ -0,0 +1,19 @@
+#!/usr/bin/env bash
+
+set -o errexit
+set -o nounset
+set -o pipefail
+
+if [ ! -L web/sites/default/settings.php ] && [ ! -e web/sites/default/settings.php ]; then
+    ln -s ../../../settings.php web/sites/default/settings.php
+fi
+
+mkdir -p web/{modules,themes}
+
+if [ ! -L web/themes/custom ] && [ ! -e web/themes/custom ]; then
+    ln -s ../../themes web/themes/custom
+fi
+
+if [ ! -L web/modules/custom ] && [ ! -e web/modules/custom ]; then
+    ln -s ../../modules web/modules/custom
+fi