Split rule documentation into separate files

doc/MD030.md

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+# MD030 - Spaces after list markers
+
+Tags: ol, ul, whitespace
+
+Aliases: list-marker-space
+
+Parameters: ul_single, ol_single, ul_multi, ol_multi (number; default 1)
+
+This rule checks for the number of spaces between a list marker (e.g. '`-`',
+'`*`', '`+`' or '`1.`') and the text of the list item.
+
+The number of spaces checked for depends on the document style in use, but the
+default is 1 space after any list marker:
+
+    * Foo
+    * Bar
+    * Baz
+
+    1. Foo
+    1. Bar
+    1. Baz
+
+    1. Foo
+       * Bar
+    1. Baz
+
+A document style may change the number of spaces after unordered list items
+and ordered list items independently, as well as based on whether the content
+of every item in the list consists of a single paragraph, or multiple
+paragraphs (including sub-lists and code blocks).
+
+For example, the style guide at
+<http://www.cirosantilli.com/markdown-styleguide/#spaces-after-marker>
+specifies that 1 space after the list marker should be used if every item in
+the list fits within a single paragraph, but to use 2 or 3 spaces (for ordered
+and unordered lists respectively) if there are multiple paragraphs of content
+inside the list:
+
+    * Foo
+    * Bar
+    * Baz
+
+    vs.
+
+    *   Foo
+
+        Second paragraph
+
+    *   Bar
+
+    or
+
+    1.  Foo
+
+        Second paragraph
+
+    1.  Bar
+
+To fix this, ensure the correct number of spaces are used after list marker
+for your selected document style.