docs: Enhance PostgreSQL client module documentation

- Add details about the new PostgreSQL installer feature.
- Include prerequisites for installer and basic operations.
- Expand test file descriptions with installer details.
- Add descriptions for installer functions.
- Include example usage for both basic operations and installer.

src/rhai_tests/postgresclient/test_print.rhai

@@ -0,0 +1,24 @@
+// Simple test script to verify that the Rhai engine is working
+
+print("Hello, world!");
+
+// Try to access the PostgreSQL installer functions
+print("\nTrying to access PostgreSQL installer functions...");
+
+// Check if the pg_install function is defined
+print("pg_install function is defined: " + is_def_fn("pg_install"));
+
+// Print the available functions
+print("\nAvailable functions:");
+print("pg_connect: " + is_def_fn("pg_connect"));
+print("pg_ping: " + is_def_fn("pg_ping"));
+print("pg_reset: " + is_def_fn("pg_reset"));
+print("pg_execute: " + is_def_fn("pg_execute"));
+print("pg_query: " + is_def_fn("pg_query"));
+print("pg_query_one: " + is_def_fn("pg_query_one"));
+print("pg_install: " + is_def_fn("pg_install"));
+print("pg_create_database: " + is_def_fn("pg_create_database"));
+print("pg_execute_sql: " + is_def_fn("pg_execute_sql"));
+print("pg_is_running: " + is_def_fn("pg_is_running"));
+
+print("\nTest completed successfully!");