Add resource detectors to compliance matrix (open-telemetry#1950)

spec-compliance-matrix.md

@@ -103,6 +103,7 @@ formats is required. Implementing more than one format is optional.
 | [Merge (v2)](specification/resource/sdk.md#merge)                                                                                           |          | +  | +    |    | +      | +    | +      |     | +    | +   | +    |       |
 | Retrieve attributes                                                                                                                         |          | +  | +    | +  | +      | +    | +      |     | +    | +   | +    | +     |
 | [Default value](specification/resource/semantic_conventions/README.md#semantic-attributes-with-sdk-provided-default-value) for service.name |          | +  | +    |    | +      | +    | +      |     |      | +   | +    |       |
+| [Resource detector](specification/resource/sdk.md#detecting-resource-information-from-the-environment) interface/mechanism                  |          | +  | +    | +  | +      | +    | +      | [-][php225]   | +    | +   | +    | +     |
 
 ## Context Propagation
 
@@ -206,3 +207,4 @@ Note: Support for environment variables is optional.
 [py1174]: https://github.com/open-telemetry/opentelemetry-python/issues/1174
 [py1437]: https://github.com/open-telemetry/opentelemetry-python/issues/1437
 [py1779]: https://github.com/open-telemetry/opentelemetry-python/issues/1779
+[php225]: https://github.com/open-telemetry/opentelemetry-php/issues/225