RDS: Add pgvector in the list of pre-installed extensions (#325)

Author: nik-localstack

src/content/docs/aws/services/rds.mdx

@@ -358,6 +358,7 @@ In addition to the `aws_*` extensions described in the sections above, LocalStac
 - `postgis_raster`
 - `postgis_tiger_geocoder`
 - `postgis_topology`
+- `pgvector`
 
 ## Resource Browser