Add type backport

Author: stfnkth

pyproject.toml

@@ -5,7 +5,12 @@ description = "Python Bindings for OpenLayersJS"
 readme = "README.md"
 authors = [{ name = "Stefan Kuethe", email = "[email protected]" }]
 requires-python = ">=3.9, <4"
-dependencies = ["anywidget>=0.9.0", "jinja2>=3.1.6", "pydantic>=2.5.3"]
+dependencies = [
+    "anywidget>=0.9.0",
+    "eval-type-backport>=0.2.2",
+ "jinja2>=3.1.6",
+ "pydantic>=2.5.3",
+]
 
 # [project.scripts]
 # openlayers = "openlayers:main"