Add codecov yaml

.codecov.yml

@@ -0,0 +1,16 @@
+# see https://docs.codecov.com/docs/codecovyml-reference
+coverage:
+  # Customize the visible colors:
+  #   <60%: red
+  #   <70%: yellow
+  #   >=70%: green
+  range: 60..70
+  status:
+    # see https://docs.codecov.com/docs/commit-status
+    project:
+      default:
+        # Allow the coverage to drop by 1%.
+        threshold: 1%
+ignore:
+  - "tests"
+  - "benches"