Add external link function and bad link text examples

[cjrace]

EDITIED:

Brief overview of changes

Added a custom wrapper for htmltools::tags$a() that makes external links easier to do and enforces accessibility.

Why are these changes being made?

External links aren't generally done well by analysts, explaining how to do them is clunky and if not done correctly they can be insecure as well as inaccessible.

Detailed description of changes

1. Added external_link() function.

In this I'm intentionally using a basic regex to check for URLs as wanted to avoid making requests every time the front end of a site using this is rendered, which would have happened if I'd used RCurl or httr's custom functions that check for a valid URL.

2. Added bad_link_text data frame with known examples of poor link text.

3. Reordered the reference list to be vaguely alphabetical (was also nicer to have cookies at the top instead of the mostly redundant tidy_code)

Additional information for reviewers

Added a couple of extra commits since raising that remove excess whitespace, pre-emptively bump the package version, and also fix up the way links show in the documentation.

Issue ticket number/s and link

No related issues, but does relate to some of the things flagged in the DAC audit.

[cjrace]

Going to add a quick extra thing to enforce .noWS = "after" as we often end up needing that for neatness

[cjrace]

Add external link function into dfeshiny

[cjrace]

Went deeper into the roxygen2 documentation and with some experimentation have managed to get the links from the function and data documentation working nicer

[rmbielby]

Few minor comments. I was looking at links on the HE LEO tab earlier so tested it out on a branch on that.

[cjrace]

Addressed all of the comments from @rmbielby, added a couple more suggestions to the bad text list from Nusrath, and used Tom's suggestion of a blanket warning for particularly short strings in the link text argument.