adding codecov reporting (#2372) [skip ci]

* adding codecov reporting

* update codecov-action to v5

* fix

---------

Co-authored-by: Dan Saunders <dan@axolotl.ai>

.coveragerc

@@ -0,0 +1,14 @@
+[run]
+source = axolotl
+omit =
+    */tests/*
+    setup.py
+
+[report]
+exclude_lines =
+    pragma: no cover
+    def __repr__
+    raise NotImplementedError
+    if __name__ == .__main__.:
+    pass
+    raise ImportError