Fixes to prepare for CRAN submission

[klmr]

• [x] Fix spurious note about “unused” R6 dependency
• [x] Fix obsolete links
• [x] Fix bundle size

Currently, the inst/doc folder is much too large, and causes CRAN to complain because the overall install size is > 5 MB.

[klmr]

One suggestion to reduce the output size of the documentation would be to run pngcrush on the images before including them into the HTML files, but that would make the vignette building more complicated. A potential solution is the ‘optout’ package: https://coolbutuseless.github.io/2020/04/03/introducing-optout-a-package-for-optimizing-graphics-output/

[banfai]

utils-tidyeval.R was generated by usethis::use_tidy_eval(), but that's obsolete now
see https://usethis.r-lib.org/reference/use_tidy_labels.html and https://github.com/r-lib/usethis/issues/1656 should we clean this up now 🎉 or make an issue to fix later 👀 ?

[klmr]

@banfai 🧹 (you can’t react with arbitrary emojis to GitHub comments, unfortunately.)

[idavydov]

I think this looks great, thanks @klmr !

Regarding optout, I think it's not on CRAN. And it's not clear how it was used in ggpattern which is now on CRAN.

[idavydov]

**Note:** due to CRAN package size limits many of these vignettes are only available in the Github version of `{ggpattern}` and the package website.

(from here and see this)

[banfai]

@banfai 🧹 (you can’t react with arbitrary emojis to GitHub comments, unfortunately.)

oops 😄

[idavydov]

@banfai once you approve, I can merge