Editing view improvements

What's Changed

fix: Indentation now persists when scrolling through large documents without requiring text edits by @jpkq8
fix: Implement embeds and images offset in edit mode by @jpkq8 (#26)
fix: React to window size changes by @jpkq8
feat: Added option "Treat highest present heading in the document as H1" by @jpkq8 (#29)

The whole release is thanks to @jpkq8 (#35)