Docs: Add docs for plot recipes

[Andy Nowacki]

There are no docs for the Plots recipes. Referring readers to the code is not sufficient to document the extra keyword arguments. Please add them to the docs somewhere.

[Charlotte Haley]

See commit that contains plots recipes documentation.

[Andy Nowacki]

Great, thanks for adding this.

Note that at the moment the README.md file links to the wrong location for the Markdown file added in 915e9bc342. I guess this can be closed once the online docs are working.

[Charlotte Haley]

After implementing the Documenter.jl solution, I think the links are now working properly. Thanks.