Rename package to revealjs.ids

Renames the fork so the IDS corporate design edition can be installed
alongside upstream rstudio/revealjs (same pattern as posterdown.ids).
Use revealjs.ids::revealjs_presentation in the R Markdown yaml header.

Changes: DESCRIPTION (Package name, Version -> 0.9.1.9009, Title notes
the IDS edition), R/utils.R package lookups, skeleton + RStudio
template identity (now 'Reveal.js Presentation (IDS CD theme)'),
README usage, GitLab CI render call, tests, examples. Old documents
referring to revealjs::revealjs_presentation need upstream revealjs
or a search/replace of the prefix.

Change-Id: Id3988b2c3fd348faca3c0951223d0b90c01741dc
diff --git a/tests/testthat/test-themes.R b/tests/testthat/test-themes.R
index d217d06..b19e1de 100644
--- a/tests/testthat/test-themes.R
+++ b/tests/testthat/test-themes.R
@@ -13,7 +13,7 @@
     testdoc <- "testdoc.Rmd"
     rmarkdown::draft(testdoc,
                      system.file("rmarkdown", "templates", "revealjs_presentation",
-                                 package = "revealjs"),
+                                 package = "revealjs.ids"),
                      create_dir = FALSE,
                      edit = FALSE)
 
@@ -31,4 +31,4 @@
 }
 
 # test all themes
-sapply(revealjs:::revealjs_themes(), test_theme)
+sapply(revealjs.ids:::revealjs_themes(), test_theme)