feat(types): Improve load type (#1584)

Allows setting `isDocument` to `false`, and passing `null` to `options`.

Author: f0x52

types/index.d.ts

@@ -267,7 +267,8 @@ declare namespace cheerio {
     version: string;
     load(
       html: string | { toString(): string },
-      options?: CheerioParserOptions
+      options?: CheerioParserOptions|null,
+      isDocument?: boolean
     ): Root;
     load(element: Element, options?: CheerioParserOptions): Root;
   }