docs: document only the IDS theme, drop stock reveal.js themes

Change-Id: I379e9fc0b46a42841eef96f17536b4c498334323
diff --git a/R/revealjs_presentation.R b/R/revealjs_presentation.R
index fa31dca..ec8a814 100644
--- a/R/revealjs_presentation.R
+++ b/R/revealjs_presentation.R
@@ -169,11 +169,8 @@
 #'   produced, with level 1 headers building horizontally and level 2 headers
 #'   building vertically. It is not recommended that you use deeper nesting of
 #'   section levels with reveal.js.
-#' @param theme Visual theme. Defaults to the dedicated IDS corporate design
-#'   theme ("ids"), which is the raison d'être of this package; the stock
-#'   reveal.js themes are available as rarely used alternatives:
-#'   `r knitr::combine_words(setdiff(revealjs_themes(), c("default", "ids")), before = '"', and = " or ")`
-#'   ("dark" is an alias for "black").
+#' @param theme Visual theme. The dedicated IDS corporate design theme
+#'   ("ids") is the default and the only supported theme.
 #' @param transition Slide transition (
 #' `r (trans <- knitr::combine_words(setdiff(revealjs_transitions(), "default"), before = '"', and = " or "))`
 #' )
diff --git a/README.Rmd b/README.Rmd
index aa034de..25c9478 100644
--- a/README.Rmd
+++ b/README.Rmd
@@ -238,7 +238,7 @@
 
 There are several options that control the appearance of revealjs presentations:
 
--   `theme` specifies the visual theme for the presentation. It defaults to the dedicated IDS corporate design theme (`"ids"`), which is the raison d'être of this package; the stock reveal.js themes are listed here only for completeness, as alternatives that will rarely be used in the IDS context: `r knitr::combine_words(setdiff(revealjs.ids:::revealjs_themes(), c("default", "ids")), before = '"', and = " or ")` (`"dark"` is an alias for `"black"`).
+-   `theme` specifies the visual theme for the presentation. The dedicated IDS corporate design theme (`"ids"`) is the default and the only supported theme.
 
 -   `highlight` specifies the syntax highlighting style. Supported styles include `r knitr::combine_words(rmarkdown:::highlighters(), before = '"', and = " or ")`. Pass null to prevent syntax highlighting.
 
@@ -253,8 +253,6 @@
     center: true
 ```
 
-Documentation of the rarely used stock themes: [reveal.js themes](https://revealjs.com/themes/)
-
 ## Slide Transitions
 
 You can use the `transition` and `background_transition` options to specify the global default slide transition style:
diff --git a/README.md b/README.md
index 1fb3f4d..ba56645 100644
--- a/README.md
+++ b/README.md
@@ -296,13 +296,9 @@
 There are several options that control the appearance of revealjs
 presentations:
 
-- `theme` specifies the visual theme for the presentation. It defaults
-  to the dedicated IDS corporate design theme (“ids”), which is the
-  raison d’être of this package; the stock reveal.js themes are listed
-  here only for completeness, as alternatives that will rarely be used
-  in the IDS context: “simple”, “dark”, “black”, “sky”, “beige”,
-  “serif”, “solarized”, “blood”, “moon”, “night”, “league”, or “white”
-  (“dark” is an alias for “black”).
+- `theme` specifies the visual theme for the presentation. The
+  dedicated IDS corporate design theme (“ids”) is the default and the
+  only supported theme.
 
 - `highlight` specifies the syntax highlighting style. Supported styles
   include “default”, “tango”, “pygments”, “kate”, “monochrome”,
@@ -321,9 +317,6 @@
     center: true
 ```
 
-Documentation of the rarely used stock themes: [reveal.js
-themes](https://revealjs.com/themes/)
-
 ## Slide Transitions
 
 You can use the `transition` and `background_transition` options to
diff --git a/man/revealjs_presentation.Rd b/man/revealjs_presentation.Rd
index 84033ba..fe4fb7e 100644
--- a/man/revealjs_presentation.Rd
+++ b/man/revealjs_presentation.Rd
@@ -69,11 +69,8 @@
 or just the body of a LaTeX document (\code{FALSE}). Note the LaTeX
 document is an intermediate file unless \code{keep_tex = TRUE}.}
 
-\item{theme}{Visual theme. Defaults to the dedicated IDS corporate design
-theme ("ids"), which is the raison d'être of this package; the stock
-reveal.js themes are available as rarely used alternatives:
-"simple", "dark", "black", "sky", "beige", "serif", "solarized", "blood", "moon", "night", "league", or "white"
-("dark" is an alias for "black").}
+\item{theme}{Visual theme. The dedicated IDS corporate design theme
+("ids") is the default and the only supported theme.}
 
 \item{transition}{Slide transition (
 "convex", "fade", "slide", "concave", "zoom", or "none"