Fix types of rule arguments

Closes GH-289. Reviewed-by: Titus Wormer <tituswormer@gmail.com>

Author: jablko

packages/unified-lint-rule/index.d.ts

@@ -19,7 +19,7 @@ export function lintRule<Tree extends Node = Node, Options = unknown>(
  name: string | RuleMeta,
  rule: Rule<Tree, Options>
 ): Plugin<
- void[] | [Options | Label | Severity] | [boolean | Label | Severity, Options],
+ void[] | [Options | [boolean | Label | Severity, (Options | undefined)?]],
  Tree
 >
 

readme.md

@@ -269,7 +269,8 @@ remark()
  .use(remarkLintUnorderedListMarkerStyle, '*')
  .use(remarkLintUnorderedListMarkerStyle, ['on', '*'])
  .use(remarkLintUnorderedListMarkerStyle, [1, '*'])
- // The following rule accepts a number, numbers *must* be passed in arrays:
+ // The following rule accepts a number:
+ .use(remarkLintMaximumLineLength, 72)
  .use(remarkLintMaximumLineLength, ['on', 72])
  .use(remarkLintMaximumLineLength, [1, 72])
 ```