Add swift to the list of `telemetry.sdk.language` (#2097)

semantic_conventions/resource/telemetry.yaml

@@ -33,6 +33,8 @@ groups:
               value: "ruby"
             - id: webjs
               value: "webjs"
+            - id: swift
+              value: "swift"
         brief: >
           The language of the telemetry SDK.
       - id: sdk.version

specification/resource/semantic_conventions/README.md

@@ -128,6 +128,7 @@ The identifier SHOULD be stable across different versions of an implementation.
 | `python` | python |
 | `ruby` | ruby |
 | `webjs` | webjs |
+| `swift` | swift |
 <!-- endsemconv -->
 
 ## Compute Unit