pyproject.toml: Add examples to sdist tarball

pyproject.toml:
Add example files to sdist tarball.

pyproject.toml

@@ -8,7 +8,8 @@ packages = [
   {include = 'arch_release_promotion'}
 ]
 include = [
-  {path = 'tests/*', format = 'sdist'}
+  {path = 'tests/*', format = 'sdist'},
+  {path = 'examples/*', format = 'sdist'},
 ]
 readme = "README.rst"
 homepage = "https://gitlab.archlinux.org/archlinux/arch-release-promotion"