Provides the engine with any helpful text around the text snippet which will be passed to the Check method.
Implementation is not required.
Declaration Syntax
Remarks
Eg. if the document contains "This is an an example piece." and Check will be called on "an example piece",
then the fact that 'an' is duplicated will not be detected. Therefore, by passing "This is an " to beforeToCheckSnippet
the checker will be able to detect that an is duplicated.