Add informational Codecov status checks

Hi, Tom from Codecov here. I noticed that you were using Codecov but weren't actually getting any notifications on pull requests. I figured it would be useful to get some idea if code being changed is being tested, but also not blocking CI/merging. Let me know if this makes sense or if we can do something that would be helpful.

.codecov.yml

@@ -8,7 +8,9 @@ coverage:
   round: down
   range: "70...100"
   status:
-    project: false
-    patch: false
+    project:
+        informational: true
+    patch:
+        informational: true
 
 comment: false