Use python 3.8-compatible type hints

Use typing's `List` and `Tuple` instead of the native `list` and `tuple` that were introduced in 3.9.

Author: Bittor Alaña

src/mkdocs_print_site_plugin/renderer.py

@@ -1,5 +1,6 @@
 import logging
 import re
+from typing import List, Tuple
 
 import jinja2
 from mkdocs.structure.toc import AnchorLink, TableOfContents
@@ -41,7 +42,7 @@ def __init__(
  def _get_items(self):
  return [i for i in self.items if not i == self.print_page]
 
- def write_combined(self) -> tuple[str, TableOfContents]:
+ def write_combined(self) -> Tuple[str, TableOfContents]:
  """
  Generates the HTML of the page that combines all page into one, while filling
  a table of contents.
@@ -78,8 +79,8 @@ def get_html_and_anchor_links_from_items(
  excluded_pages: list,
  level: int = 0,
  prefix: str = "",
- heading_styles: list[str] = [],
- ) -> tuple[str, list[AnchorLink]]:
+ heading_styles: List[str] = [],
+ ) -> Tuple[str, List[AnchorLink]]:
  """
  Get all the HTML and anchor links from the pages.
  """