Refactor to simplify types w/ ReadonlyArray

Closes GH-20.

Reviewed-by: Remco Haszing <[email protected]>
Reviewed-by: Christian Murphy <[email protected]>
Reviewed-by: Titus Wormer <[email protected]>

Author: JounQin

lib/index.js

@@ -27,7 +27,7 @@
  *
  *   Note: `Node` is included as it is common but is not indexable.
  *
- * @typedef {Array<Props | TestFunction | string> | ReadonlyArray<Props | TestFunction | string> | Props | TestFunction | string | null | undefined} Test
+ * @typedef {ReadonlyArray<Props | TestFunction | string> | Props | TestFunction | string | null | undefined} Test
  *   Check for an arbitrary node.
  *
  * @callback TestFunction
@@ -67,7 +67,6 @@ export const is =
   /**
    * @type {(
    *   (<Condition extends ReadonlyArray<string>>(node: unknown, test: Condition, index?: number | null | undefined, parent?: Parent | null | undefined, context?: unknown) => node is Node & {type: Condition[number]}) &
-   *   (<Condition extends Array<string>>(node: unknown, test: Condition, index?: number | null | undefined, parent?: Parent | null | undefined, context?: unknown) => node is Node & {type: Condition[number]}) &
    *   (<Condition extends string>(node: unknown, test: Condition, index?: number | null | undefined, parent?: Parent | null | undefined, context?: unknown) => node is Node & {type: Condition}) &
    *   (<Condition extends Props>(node: unknown, test: Condition, index?: number | null | undefined, parent?: Parent | null | undefined, context?: unknown) => node is Node & Condition) &
    *   (<Condition extends TestFunction>(node: unknown, test: Condition, index?: number | null | undefined, parent?: Parent | null | undefined, context?: unknown) => node is Node & Predicate<Condition, Node>) &