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.

.gitignore

@@ -1,16 +1,6 @@
-html/
-vendor/
-
-!content/
-
-web/*
-!web/assets/
-web/assets/*
-!web/assets/images/
-!web/themes/
-web/themes/*
-!web/themes/custom/
-web/themes/custom/*
-!web/themes/custom/opdavies/
-
-recipes/*/content
+/.editorconfig
+/.gitattributes
+/drush
+/html
+/vendor/
+/web