* use logical `NA` that can be cast to character

* chore: Use ggplot2's default color scale `na.value`

* chore: document()

* chore: Also set `na.value = "grey50"` in `scale_xaringan_discrete()`.

* chore: Add news item

---------

Co-authored-by: Garrick Aden-Buie <garrick@adenbuie.com>

* Increment version number to 0.4.3

* chore: add cran comments

* Fix indents and invisible characters (GitHub Actions)

* Re-build README.Rmd (GitHub Actions)

* Re-build index.Rmd (GitHub Actions)

* chore: urlchecker::url_update()

* chore: align and register s3 print methods

* tests: Update and fix tests

* docs: update link in thanks

---------

Co-authored-by: gadenbuie <gadenbuie@users.noreply.github.com>

For #36

Fixes #36

Updates color examples and adds left-column headings demo to skeleton

Avoids note for long argument length and allows for more consistent checking if supplied arguments are default values

Fixes #31

Now, font size is inherited from `base_font_size` which should be in absolute units.

See google/fonts issue number 1223

* fix style of ggplot2, xaringan pkg refs
* fix name of theme_xaringan_restore_defaults()

not working because {colorspace} doesn't force evaluation of
input arguments to scale_color_xxx_xxx() before passing down
to sequential_hcl()

...and renamed from get_xaringanthemer_value()