docs(resource-detector-container): update readme for container resource detector (#2061)

Refs: #2055
Signed-off-by: maryliag <[email protected]>

Author: maryliag

detectors/node/opentelemetry-resource-detector-container/README.md

@@ -28,7 +28,15 @@ const tracerProvider = new NodeTracerProvider({ resource });
 
 ## Available detectors
 
-- `containerDetector`: Populates `container.id` for processes running on containers supporting : docker( cgroup v1 or v2 ) or with containerd
+This package uses `@opentelemetry/semantic-conventions` version `1.22+`, which implements Semantic Convention [Version 1.7.0](https://github.com/open-telemetry/opentelemetry-specification/blob/v1.7.0/semantic_conventions/README.md)
+
+### ContainerDetector
+
+Populates `container.id` for processes running on containers supporting : docker( cgroup v1 or v2 ) or with containerd
+
+| Resource Attribute |  Description                                                                                                                             |
+|--------------------|------------------------------------------------------------------------------------------------------------------------------------------|
+| `container.id`     | Value parsed from file `/proc/self/cgroup` (cgroup v1). If it doesn't exist, parse the value from file `/proc/self/mountinfo` (cgroup v2)|
 
 ## Useful links