Add Bookstack blueprint with Docker Compose and configuration files

- Introduced Docker Compose setup for Bookstack service, including environment variables and volume configuration.
- Added logo for Bookstack.
- Created template.toml for Bookstack with default variables for configuration.

blueprints/bookstack/template.toml

@@ -0,0 +1,15 @@
+[variables]
+main_domain = "${domain}"
+db_password = "${password:16}"
+app_key = "${password:32}"
+
+[config]
+[[config.domains]]
+serviceName = "bookstack"
+port = 80
+host = "${main_domain}"
+
+[config.env]
+DOMAIN = "${main_domain}"
+DB_PASSWORD = "${db_password}"
+APP_KEY = "${app_key}"