Added customizable UI for Instruct mode (#26)

* progress

* more progress

* even more progress (getting close)

* 95% there!

* fixup to use proper tags

* push the polyfill fix onto existing code to prevent older browsers from breaking

* Moved 'Customize UI' button under 'Gear' menu, and made it only appear in Instruct Mode

* Minor fix to account for instruct tags in preview mode

* Added support of UI Customization for mobile (no live preview)

* Made images be compressed and serialized only once. Added support for compressing PNG images to support transparency.

* Removed placeholder help icon from Portrait Style

* Fixed bug preventing 'Edit' button to be clicked on new stories

* Updated initial values

* Minor design tweak for preparing new AI reply

* Moved code around

* Added comments

* minor real-time-update tweak on portrait swap

* Fixed rendering of embedded HTML parts.

* Fixed bug requiring enhanced_chat_UI to be ticked to render enhanced_instruct_UI

* Increased responsiveness of Preview Panel.

* fixup for last commit (Increased responsiveness of preview panel)

* fixed all the wonky layout issues with aesthetic instruct. settings persist still need improvement, cancel still not working

* Fixed OK/Cancel buttons

* Disabling 'persist_session' now does not load instruct UI customization settings

* OK/Cancel fixup.. oof

* polyfill incompatibles

* WIP layouting and portraits improvements

* data range sanitization

* cleanup all remaining issues and prepare for squashmerge

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Co-authored-by: Concedo <Concedo@noreply.com>