chore: Create docker-compose.yml do match CONTRIBUTING.md (#918)

Signed-off-by: Philipp Fehre <philipp.fehre@mollie.com>

Author: sideshowcoder

providers/flagd/CONTRIBUTING.md

@@ -23,7 +23,7 @@ In vscode for instance, the following settings are recommended:
 The continuous integration runs a set of [gherkin e2e tests](https://github.com/open-feature/test-harness/blob/main/features/evaluation.feature) using [`flagd`](https://github.com/open-feature/flagd). These tests do not run with the default maven profile. If you'd like to run them locally, you can start the flagd testbed with
 
 ```
-docker-compose up
+docker compose up
 ```
 and then run 
 ```
@@ -36,4 +36,4 @@ FLAGD_HOST=192.168.100.1 mvn test -P e2e
 ```
 
 If test-harness is being updated, commit the changes before running `mvn`.
-Otherwise, uncommitted changes will be overridden by maven test plugins.
+Otherwise, uncommitted changes will be overridden by maven test plugins.

providers/flagd/docker-compose.yml

@@ -0,0 +1,5 @@
+services:
+  flagd:
+    build:
+      context: ./test-harness
+      dockerfile: flagd/Dockerfile