Enable to mask texts (#73)

* chore: reorder options

* feat: enable to mask texts

* feat: add the default mask function

* refactor: rename options to identify the difference between  mask text and mask input

* test: add tests about masking

src/types.ts

@@ -105,3 +105,5 @@ export type SlimDOMOptions = Partial<{
   headMetaAuthorship: boolean;
   headMetaVerification: boolean;
 }>;
+
+export type MaskTextFn = (text: string) => string;