Push latest tag on main branch

.gitlab-ci.yml

@@ -111,6 +111,13 @@ workflow:
       ]]; then
         docker tag "${latest_image_name}" "usgs/${CI_PROJECT_NAME}:${ENVIRONMENT}-latest";
         docker push "usgs/${CI_PROJECT_NAME}:${ENVIRONMENT}-latest";
+
+        if [[ ${CI_COMMIT_REF_SLUG} == "${CI_DEFAULT_BRANCH" ]]; then
+          docker tag \
+              "usgs/${CI_PROJECT_NAME}:${ENVIRONMENT}-latest" \
+              "usgs/${CI_PROJECT_NAME}:latest";
+          docker push "usgs/${CI_PROJECT_NAME}:latest";
+        fi
       fi
     - |
       printf "