This function auto-detects the location of your package logo (with the name
logo.svg (recommended format) or logo.png, created with usethis::use_logo())
and runs it through the https://realfavicongenerator.net API to build a
complete set of favicons with different sizes, as needed for modern web usage.
You only need to run the function once. The favicon set will be stored in
pkgdown/favicon and copied by init_site() to the relevant location when
the website is rebuilt.
Once complete, you should add pkgdown/ to .Rbuildignore to avoid a NOTE
during package checking. (usethis::use_logo() does this for you!)