Make HTML codebook

[mbcann01]

Currently, codebook uses the flextable package to create codebooks as a Word document. I would like to add the option of creating codebooks as HTML documents that can be hosted on, for example, GitHub pages.

• [ ] Wrap the current codebook() code inside a new function codebook_word(). Keep in in codebook.R. Create a new function codebook_html() also written in codebook.R. All the codebook function does is choose one of those two function.
• [ ] Set version to 0.3.0

[edambo]

I've updated the codebook function and created the functions codebook_word and codebook_html.