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

doc/md041.md

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+# MD041 - First line in a file should be a top-level heading
+
+Tags: headers, headings
+
+Aliases: first-line-h1, first-line-heading
+
+Parameters:
+
+* `front_matter_title`: RegExp for matching title in front matter (`string`, default `^\s*title\s*[:=]`)
+* `level`: Heading level (`integer`, default `1`)
+
+This rule is intended to ensure documents have a title and is triggered when
+the first line in the file isn't a top-level (h1) heading:
+
+```markdown
+This is a file without a heading
+```
+
+To fix this, add a top-level heading to the beginning of the file:
+
+```markdown
+# File with heading
+
+This is a file with a top-level heading
+```
+
+Because it is common for projects on GitHub to use an image for the heading of
+`README.md` and that is not well-supported by Markdown, HTML headings are also
+permitted by this rule. For example:
+
+```markdown
+<h1 align="center"><img src="https://placekitten.com/300/150"/></h1>
+
+This is a file with a top-level HTML heading
+```
+
+Note: The `level` parameter can be used to change the top-level (ex: to h2) in cases
+where an h1 is added externally.
+
+If [YAML](https://en.wikipedia.org/wiki/YAML) front matter is present and
+contains a `title` property (commonly used with blog posts), this rule will not
+report a violation. To use a different property name in the front matter,
+specify the text of a regular expression via the `front_matter_title` parameter.
+To disable the use of front matter by this rule, specify `""` for `front_matter_title`.
+
+Rationale: The top-level heading often acts as the title of a document. More
+information: <https://cirosantilli.com/markdown-style-guide#top-level-header>.