Add legacy SDK compatibility example

Author: fern-api[bot]

examples/README.md

@@ -0,0 +1,29 @@
+# Square legacy compatiblity
+
+While the new SDK has a lot of improvements, we at Square understand that
+it takes time to upgrade when there are breaking changes. To make the
+migration easier, the new SDK can be used alongisde legacy SDK, which is
+now published as `squareup_legacy`. 
+
+This example demonstrates how you can use the legacy SDK alongside the new
+SDK inside a single file.
+
+```python
+from square import Square
+from square_legacy.client import Client as LegacySquare
+
+
+def main():
+    client = Square(token="<YOUR_API_KEY>")
+    legacy_client = LegacySquare(access_token="<YOUR_API_KEY>")
+
+    ...
+```
+
+You can run the example with the following:
+
+```sh
+cd example
+poetry install
+poetry run run-example
+```