add sonar-project.properties

Signed-off-by: Alex Meijer <ameijer@kubecost.com>

sonar-project.properties

@@ -0,0 +1,5 @@
+sonar.projectKey=opencost_opencost
+sonar.sources=pkg
+sonar.go.coverage.reportPaths=coverage.out,coverage/coverage.out
+sonar.test.inclusions=**/*_test.go
+sonar.coverage.exclusions=**/*_test.go