Add typing metadata and include py.typed in sdist

This commit marks the package as typed in the classifiers and ensures `py.typed` is included in the source distribution. This improves compatibility with type checkers and enforces better type safety for users.

Author: Hector Oliveros

py.typed

@@ -35,6 +35,7 @@ classifiers = [
     "Programming Language :: Python :: 3.12",
     "Programming Language :: Python :: 3.13",
     "Topic :: Software Development :: Libraries :: Python Modules",
+    "Typing :: Typed",
 ]
 [dependency-groups]
 dev = [
@@ -72,7 +73,10 @@ Homepage = "http://freeopcua.github.io/"
 Repository = "https://github.com/FreeOpcUa/opcua-asyncio"
 
 [tool.hatch.build.targets.sdist]
-include = ["/asyncua"]
+include = [
+    "/asyncua",
+    "/asyncua/py.typed"
+]
 
 [tool.pytest.ini_options]
 log_cli = false