chore: add requirements section

Author: vishalm0509

docs/install/olake-ui/index.mdx

@@ -136,6 +136,13 @@ This will create and use `/custom/path/to/olake-data` instead of the default `./
 
 OLake supports using an **external PostgreSQL instance** instead of the built-in Postgres service included in the docker-compose file. PostgreSQL stores all job data, configurations, sync state, and Temporal workflow data.
 
+**Requirements:**
+
+- PostgreSQL 12+ with `btree_gin` extension enabled
+- This can be enabled with `CREATE EXTENSION IF NOT EXISTS btree_gin;`, then run `\dx` to verify if its enabled.
+- Both OLake and Temporal databases created on the PostgreSQL instance
+- Network connectivity from the machine to the PostgreSQL instance
+
 **Configure `docker-compose.yml`**
 
 Within the compose file, an extension field named `x-db-envs` defines all database configuration values used by OLake and Temporal. These values can be modified to point to the external PostgreSQL instance.