update pyproject.toml to distribute all headers in subfolders of `include`

pyproject.toml

@@ -89,7 +89,8 @@ build-backend = "setuptools.build_meta"
 
 [tool.setuptools.package-data]
 pystencils = [
-    "include/*.h",
+    "include/**/*.h",
+    "include/**/*.hpp",
     "jit/cpu/*.tmpl.cpp",
     "boundaries/createindexlistcython.pyx"
 ]