docs: Fix warnings in re pattern and update py-gfm version

1. wipe out syntaxwarnings of "invalid escape sequence '\s'"
2. update py-gfm version to fit python3.8+

Signed-off-by: Ju Nan <junan76@163.com>

docs/_klipper3d/mkdocs-requirements.txt

@@ -6,5 +6,5 @@ mkdocs-simple-hooks==0.1.3
 mkdocs-exclude==1.0.2
 mdx-truly-sane-lists==1.2
 mdx-breakless-lists==1.0.1
-py-gfm==1.0.2
+py-gfm==2.0.0
 markdown==3.3.7

docs/_klipper3d/mkdocs_hooks.py

@@ -21,11 +21,11 @@ def transform(markdown: str, page, config, files):
     for i in range(len(lines)):
         line_out = lines[i]
         in_code_block = (in_code_block +
-            len(re.findall("\s*[`]{3,}", line_out))) % 2
+            len(re.findall(r"\s*[`]{3,}", line_out))) % 2
         if not in_code_block:
             line_out = line_out.replace('](../',
                                         f"]({config['repo_url']}blob/master/")
-            line_out = re.sub("\\\s*$", "<br>", line_out)
+            line_out = re.sub(r"\\\s*$", "<br>", line_out)
             # check that lists at level 0 are not indented
             # (no space before *|-|1.)
             if re.match(r"^[^-*0-9 ]", line_out):