Add codecov configuration to enable PR comments

.codecov.yml

@@ -0,0 +1,10 @@
+# show coverage in CI status, not as a comment. Never consider it a failure.
+comment: off
+coverage:
+  status:
+    project:
+      default:
+        target: 0%
+    patch:
+      default:
+        target: 0%