Add Feature to Sync Scrolling between Editor and Preview Panes

[AdKnow]

Added Feature to Sync Scrolling as a toggle with the shortcut 'r'.

[metaory]

thanks for your PR @AdKnow ,
can you help with merge conflict?

I like the simplicity of not worrying about markdown render, but I wonder how accurate the results are,

by markdown render I mean the produced rendered markdown doesnt necessarily correspond one to one with the raw editor content

like 4 lines of raw markdown might render to just one line in preview

[metaory]

implemented a more compressive scroll sync v1.18.0
@AdKnow