Vendor reveal.js 5.2.1 (from 5.1.0)

Contains the upstream 5.2.x feature set, most notably the lightbox
(data-preview-image/data-preview-video opens media full-size in an
overlay), controls: "speaker-only", search API extensions and
speaker-view fixes. The package's local additions are carried over
unchanged: IDS theme (ids.css/ids.scss), extra theme fonts,
chalkboard/customcontrols/menu plugins, and the 1280x720 default
slide size (patched in js/config.js and the dist bundles).

Also fixes a pre-existing fork bug (unrelated to the upgrade): the
slidechanged Highcharts resize hook in default.html now checks that
Highcharts exists, no longer throwing in decks without highcharter.

Docs: README (Rmd + rendered md) gained a short Lightbox section,
NEWS.md notes the library bump.

Verified: examples/ids.html and examples/simple.html re-render and run
error-free through all 13/5 slides (Reveal.VERSION = 5.2.1); lightbox
opens on click and closes with Esc in a dedicated test deck.

Change-Id: I0751129dfb0c9d20b56241377905876314a26011
diff --git a/inst/reveal.js-5.2.1/.codespellrc b/inst/reveal.js-5.2.1/.codespellrc
new file mode 100644
index 0000000..bbdb2ce
--- /dev/null
+++ b/inst/reveal.js-5.2.1/.codespellrc
@@ -0,0 +1,8 @@
+[codespell]
+# Ref: https://github.com/codespell-project/codespell#using-a-config-file
+skip = .git*,package-lock.json,*.css,.codespellrc
+check-hidden = true
+# Ignore super long lines -- must be minimized etc, acronyms
+# and some near hit variables
+ignore-regex = ^.{120,}|\b(currentY|FOM)\b
+# ignore-words-list =