Use python 3.10 and fix types

ops_bot/util/template.py

@@ -14,6 +14,7 @@
 # You should have received a copy of the GNU Affero General Public License
 # along with this program.  If not, see <https://www.gnu.org/licenses/>.
 import os.path
+from pathlib import Path
 from typing import Any, Callable, Dict, List, Tuple, Union
 
 from jinja2 import BaseLoader
@@ -24,12 +25,12 @@ from ops_bot import get_project_root
 from ops_bot.util import markdown
 
 
-def sync_read_file(path: str) -> str:
+def sync_read_file(path: Union[Path, str]) -> str:
     with open(path) as file:
         return file.read()
 
 
-def sync_list_files(directory: str) -> list[str]:
+def sync_list_files(directory: Union[Path, str]) -> list[str]:
     return os.listdir(directory)
 
 
@@ -108,7 +109,7 @@ class TemplateProxy:
 
 
 class PluginTemplateLoader(BaseLoader):
-    directory: str
+    directory: Path
     macros: str
 
     def __init__(self, base: str, directory: str) -> None: