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

doc/md020.md

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+# MD020 - No space inside hashes on closed atx style heading
+
+Tags: atx_closed, headers, headings, spaces
+
+Aliases: no-missing-space-closed-atx
+
+Fixable: Most violations can be fixed by tooling
+
+This rule is triggered when spaces are missing inside the hash characters
+in a closed atx style heading:
+
+```markdown
+#Heading 1#
+
+##Heading 2##
+```
+
+To fix this, separate the heading text from the hash character by a single
+space:
+
+```markdown
+# Heading 1 #
+
+## Heading 2 ##
+```
+
+Note: this rule will fire if either side of the heading is missing spaces.
+
+Rationale: Violations of this rule can lead to improperly rendered content.