Add configuration option for PDF side-by-side mode

dev-server/templates/client-config.js.mustache

@@ -2,6 +2,7 @@
   window.hypothesisConfig = function() {
     return {
       // enableExperimentalNewNoteButton: true,
+      enableExperimentalPDFSideBySide: true,
       // showHighlights: 'always',
       // theme: 'clean',
 

src/annotator/config/index.js

@@ -22,6 +22,13 @@ export default function configFrom(window_) {
     enableExperimentalNewNoteButton: settings.hostPageSetting(
       'enableExperimentalNewNoteButton'
     ),
+    enableExperimentalPDFSideBySide: settings.hostPageSetting(
+      'enableExperimentalPDFSideBySide',
+      {
+        coerce: toBoolean,
+        defaultValue: false,
+      }
+    ),
     group: settings.group,
     focus: settings.hostPageSetting('focus'),
     theme: settings.hostPageSetting('theme'),