Add visualLineSide helper

FEATURE: `EditorView.visualLineSide` can be used to find the visual end or start of
a line with bidirectional text.

src/cursor.ts

@@ -273,7 +273,7 @@ export function moveByChar(view: EditorView, start: SelectionRange, forward: boo
       char = "\n"
       line = view.state.doc.line(line.number + (forward ? 1 : -1))
       spans = view.bidiSpans(line)
-      next = EditorSelection.cursor(forward ? line.from : line.to)
+      next = view.visualLineSide(line, !forward)
     }
     if (!check) {
       if (!by) return next

src/editorview.ts

@@ -661,6 +661,16 @@ export class EditorView {
     return skipAtoms(this, start, moveByChar(this, start, forward, initial => byGroup(this, start.head, initial)))
   }
 
+  /// Get the cursor position visually at the start or end of a line.
+  /// Note that this may differ from the _logical_ position at its
+  /// start or end (which is simply at `line.from`/`line.to`) if text
+  /// at the start or end goes against the line's base text direction.
+  visualLineSide(line: Line, end: boolean) {
+    let order = this.bidiSpans(line), dir = this.textDirectionAt(line.from)
+    let span = order[end ? order.length - 1 : 0]
+    return EditorSelection.cursor(span.side(end, dir) + line.from, span.forward(!end, dir) ? 1 : -1)
+  }
+
   /// Move to the next line boundary in the given direction. If
   /// `includeWrap` is true, line wrapping is on, and there is a
   /// further wrap point on the current line, the wrap point will be