Add docker command to the readme file (#69)

Author: dilankavishka

README.md

@@ -32,6 +32,11 @@ and easy-to-use framework for simulating user load and measuring system performa
 To run the performance tests locally, follow these steps:
 
 1. Start OpenMRS on port 80. (Use the docker file: [src/test/resources/docker-compose.yml](src/test/resources/docker-compose.yml) It contains demo patients for the test. [Learn more](#generating-demo-patient-data))
+
+For using the docker file, run the following command:
+```bash
+   docker compose -f src/test/resources/docker-compose.yml up
+```
 2. Execute the following command in your terminal:
 
    **Standard** `export SIMULATION_PRESET='standard' && ./mvnw gatling:test` \