Update MD022/blanks-around-headings to allow specifying a different number of blank lines for each heading level (fixes #504).

doc/md022.md

@@ -6,8 +6,8 @@ Aliases: `blanks-around-headers`, `blanks-around-headings`
 
 Parameters:
 
-- `lines_above`: Blank lines above heading (`integer`, default `1`)
-- `lines_below`: Blank lines below heading (`integer`, default `1`)
+- `lines_above`: Blank lines above heading (`integer|integer[]`, default `1`)
+- `lines_below`: Blank lines below heading (`integer|integer[]`, default `1`)
 
 Fixable: Some violations can be fixed by tooling
 
@@ -36,12 +36,16 @@ Some more text
 ```
 
 The `lines_above` and `lines_below` parameters can be used to specify a
-different number of blank lines (including `0`) above or below each heading. If
-the value `-1` is used for either parameter, any number of blank lines is
-allowed.
+different number of blank lines (including `0`) above or below each heading.
+If the value `-1` is used for either parameter, any number of blank lines is
+allowed. To customize the number of lines above or below each heading level
+individually, specify a `number[]` where values correspond to heading levels
+1-6 (in order).
 
-Note: If `lines_above` or `lines_below` are configured to require more than one
-blank line, [MD012/no-multiple-blanks](md012.md) should also be customized.
+Notes: If `lines_above` or `lines_below` are configured to require more than one
+blank line, [MD012/no-multiple-blanks](md012.md) should also be customized. This
+rule checks for *at least* as many blank lines as specified; any extra blank
+lines are ignored.
 
 Rationale: Aside from aesthetic reasons, some parsers, including `kramdown`,
 will not parse headings that don't have a blank line before, and will parse them