feat: Additional embed integrations (#3398)

* feat: Gliffy integration

* feat: JSFiddle integration

* feat: Otter.ai integration

* Optimised images with calibre/image-actions

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

shared/styles/theme.ts

@@ -92,6 +92,7 @@ export const base = {
 
 export const light = {
   ...base,
+  isDark: false,
   background: colors.white,
   secondaryBackground: colors.warmGrey,
   link: colors.primary,
@@ -149,6 +150,7 @@ export const light = {
 
 export const dark = {
   ...base,
+  isDark: true,
   background: colors.almostBlack,
   secondaryBackground: colors.black50,
   link: "#137FFB",