Hello docs: state assumtions in the Introduction section
Hello docs: grammar
Hello docs: update Defining the Pattern section
Hello docs: add a temporary word of caution at the top
Hello docs: "Adding Configuration Options to a Pattern" section
Hello docs: changes to "Using the Pattern on a Page" section
Hello docs: the Options Format section
Hello docs: Nesting the Options section
Hello docs: add title of the new section (Writing Tests)