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/helpers.R b/tests/testthat/helpers.R
index ce5d6c4..894f680 100644
--- a/tests/testthat/helpers.R
+++ b/tests/testthat/helpers.R
@@ -9,7 +9,7 @@
   # TODO: Use `rmarkdown::draft()` when rmarkdown 2.12 is out.  
   pkg_file <- getFromNamespace("pkg_file", "rmarkdown")
   template_path <- pkg_file("rmarkdown", "templates", "revealjs_presentation", 
-                            package = "revealjs")
+                            package = "revealjs.ids")
   rmarkdown::draft(path, template_path, edit = FALSE)
 }