Improve sync scrolling resolution

[alcarney]

What would you like to see

Right now sync scrolling works, but depending on document content the resolution is a little coarse. This can be tackled on two fronts

• Extend the line number transform to pass through line numbers from more node types
• Update the sync logic in webview.js to search for the nearest matching number, (it currently only works if asked to scroll to a line number that matches exactly with the available numbers)