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/examples/ids.Rmd b/examples/ids.Rmd
index 34c1f5f..4f6ea73 100644
--- a/examples/ids.Rmd
+++ b/examples/ids.Rmd
@@ -7,7 +7,7 @@
 institute: "IDS Mannheim"
 date: "`r paste0('Mannheim, ', Sys.Date())`"
 output: 
-  revealjs::revealjs_presentation:
+  revealjs.ids::revealjs_presentation:
     reveal_plugins: 
       - search
       - zoom
diff --git a/examples/simple.Rmd b/examples/simple.Rmd
index 3ab2404..5565beb 100644
--- a/examples/simple.Rmd
+++ b/examples/simple.Rmd
@@ -1,7 +1,7 @@
 ---
 title: "Untitled"
 output: 
-  revealjs::revealjs_presentation:
+  revealjs.ids::revealjs_presentation:
     self_contained: false
     reveal_plugins: 
       - search