link url and orcid for authors in DESCRIPTION

[TimTaylor]

Initial poc for:

• linking an authors name to their URL.
• linking to ORCiD

@yihui - I'm marking this as draft for now but wanted to share before I go down an unnecessary rabbit holes.

Questions:

1. I'm not very familiar with html/css so have hardcoded the same css that is used on CRAN. I guess you would want this moved elsewhere / handled differently but I'm not sure how you like to do this?
2. I've bundled the svg (again the one used by CRAN) and currently it requires a user to have it in their site directory. I think it may be better to have the svg incorporated directly, e.g. <img src='data:image/svg+xml;utf8,<svg ... > ... </svg>'> but I was unable to get this working (likely due to my ignorance of html and css). If you think that would be a better approach let me know and I'll try again.

I probably can't look at this again for a couple of days, but let me know if you have thoughts comments and I'll update when I can (that said, feel free to pick this up and alter should you wish).

[TimTaylor]

I've noted that the check has failed because I'm using raw character constants (i.e. r"()" syntax). I'll update this as needed.

[yihui]

Thanks! It looks like you have finished the majority of the work. I can pick it up from here and get it done in a few minutes.