API for horizontal scroll position in TextEditor

<!-- ⚠️⚠️ Do Not Delete This! feature_request_template ⚠️⚠️ --> I would pleased to have an API on `TextEditor` allowing to get and set the horizontal scroll position, as well as an event to react to changes. I am developing an extension which compares files in multiple text editors and having synchronized scrolling would be great for UX. Currently, we have this API for *vertical* scrolling: ```typescript readonly TextEditor.visibleRanges: Range[]; TextEditor.revealRange(range: Range, revealType?: TextEditorRevealType): void; window.onDidChangeTextEditorVisibleRanges: Event<TextEditorVisibleRangesChangeEvent>; ``` For my purposes, it would be more suitable to have an API not tied to text `Range`s, otherwise one would first need to find a visible line in the editor long enough to scroll to a certain positon within it. Maybe something like: ```typescript readonly TextEditor.horizontalStart: number; readonly TextEditor.horizontalEnd: number; TextEditor.setHorizontalStart(start: number, cause: unknown); TextEditor.onDidHorizontalVisibleRangeChange: Event<{editor: TextEditor, cause: unknown}>; ``` …where `horizontalStart`, `horizontalEnd` and `start` should be floating point numbers. `cause` is meant for preventing cycles of events when synchronizing scroll positions.