Add comment explaining situation

.codecov.yml

@@ -1,3 +1,7 @@
+# We'd like to place this file to the .config/ folder as well,
+# however Codecov doesn't support it yet (or is buggy, see
+# https://github.com/codecov/codecov-action/issues/1465)
+
 # Ignore test files themselves in the Codecov report
 # see: https://about.codecov.io/blog/should-i-include-test-files-in-code-coverage-calculations/
 ignore: