Add codecov output

Author: Ignacio Bonafonte

.github/workflows/BuildAndTest.yml

@@ -9,7 +9,11 @@ jobs:
 
     steps:
     - uses: actions/checkout@v2
-    - name: Build for macOS
-      run: swift build
-    - name: Test for macOS
-      run: swift test
+    - name: Build and Test for macOS
+      run: swift test --enable-code-coverage
+    - name: Upload Code coverage
+      run: |
+        curl -Os https://uploader.codecov.io/latest/macos/codecov
+        chmod +x codecov
+        codecovpath=$(swift test --show-codecov-path)
+        ./codecov -f $codecovpath

README.md

@@ -1,6 +1,8 @@
 # opentelemetry-swift
 
 [![CI](https://github.com/open-telemetry/opentelemetry-swift/actions/workflows/BuildAndTest.yml/badge.svg)](https://github.com/open-telemetry/opentelemetry-swift/actions/workflows/BuildAndTest.yml?query=branch%3Amain+)
+[![codecov](https://codecov.io/gh/open-telemetry/opentelemetry-swift/branch/master/graph/badge.svg)](https://codecov.io/gh/open-telemetry/opentelemetry-swift)
+
 
 
 A swift [OpenTelemetry](https://opentelemetry.io/) client