add codecov setting (#198)

Author: Red-Portal

.codecov.yml

@@ -0,0 +1,14 @@
+# https://docs.codecov.io/docs/codecovyml-reference
+
+# We have
+#   * 4 workflows for each AD backends
+#   * 1 separate workflow for non-AD tests
+#   * 3 operating systems
+#   * 2 Julia versions
+# In total this is 3 x 2 x (4 + 1) = 30 tests
+codecov:
+  branch: main
+  notify:
+    after_n_builds: 30
+comment:
+  after_n_builds: 30