docs: Setup mkdocs with mkdocs-material theme

This changes the framework used to generate the klipper3d site.

Signed-off-by: Damien Martin <damlobster@gmail.com>

docs/_klipper3d/mkdocs_hooks.py

@@ -0,0 +1,18 @@
+import re
+
+def transform(markdown: str, page, config, files):
+    in_list = False
+    lines = markdown.splitlines()
+    for i in range(len(lines)):
+        lines[i] = lines[i].replace('](../',
+                                    f"]({config['repo_url']}blob/master/")
+        lines[i] = re.sub(r"\\", "<br>", lines[i])
+        # check that lists at level 0 are not indented (no space before *|-|1.)
+        if len(lines[i]) == 0:
+            in_list = False
+        elif re.match(r"^(\*|-|\d+\.) ", lines[i]):
+            in_list = True
+        if not in_list:
+            lines[i] = re.sub(r"^\s+(\*|-|\d+\.) ", r"\1 ", lines[i])
+    output = "\n".join(lines)
+    return output