Add Markdown linter

Add Markdown linter (pymarkdown) to pre-commit.
Adapt current markdown files to fulfill linter rules.

Signed-off-by: Bobby Noelte <b0661n0e17e@gmail.com>

.pre-commit-config.yaml

@@ -33,3 +33,12 @@ repos:
           - "pandas-stubs==2.2.3.241009"
           - "numpy==2.1.3"
         pass_filenames: false
+  - repo: https://github.com/jackdewinter/pymarkdown
+    rev: main
+    hooks:
+      - id: pymarkdown
+        files: ^docs/
+        exclude: ^docs/_generated
+        args:
+          - --config=docs/pymarkdown.json
+          - scan