Generate Rules.md and md###.md files from metadata, improve Parameters documentation by referencing schema.

doc-build/md033.md

@@ -0,0 +1,17 @@
+This rule is triggered whenever raw HTML is used in a Markdown document:
+
+```markdown
+<h1>Inline HTML heading</h1>
+```
+
+To fix this, use 'pure' Markdown instead of including raw HTML:
+
+```markdown
+# Markdown heading
+```
+
+Note: To allow specific HTML elements, use the `allowed_elements` parameter.
+
+Rationale: Raw HTML is allowed in Markdown, but this rule is included for
+those who want their documents to only include "pure" Markdown, or for those
+who are rendering Markdown documents into something other than HTML.