fix: make beartype optional

Author: KyleKing

mdformat_admon/plugin.py

@@ -4,13 +4,17 @@
 
 import textwrap
 
-from beartype.typing import Mapping
 from markdown_it import MarkdownIt
 from mdformat.renderer import RenderContext, RenderTreeNode
 from mdformat.renderer.typing import Render
 
 from .mdit_plugins import python_markdown_admon_plugin
 
+try:
+    from beartype.typing import Mapping
+except ImportError:
+    from collections.abc import Mapping
+
 
 def update_mdit(mdit: MarkdownIt) -> None:
     """Update the parser with supported formats."""

tox.ini

@@ -26,7 +26,9 @@ extras = dev
 commands = pre-commit run --config .pre-commit-test.yaml {posargs:--all-files --verbose --show-diff-on-failure}
 
 [testenv:mypy]
-deps = mypy
+deps = 
+    beartype
+    mypy
 commands = mypy ./mdformat_admon
 
 [testenv:ruff]