Allow Plot::link_cursor to accept impl Into<Vec2b>

Updates the `link` argument to the `impl Into<Vec2b>` to be
consistent with `link_axis`. This makes it slightly cleaner
to use.

egui_plot/src/lib.rs

@@ -587,8 +587,8 @@ impl<'a> Plot<'a> {
     /// Add this plot to a cursor link group so that this plot will share the cursor position with other plots
     /// in the same group. A plot cannot belong to more than one cursor group.
     #[inline]
-    pub fn link_cursor(mut self, group_id: impl Into<Id>, link: Vec2b) -> Self {
-        self.linked_cursors = Some((group_id.into(), link));
+    pub fn link_cursor(mut self, group_id: impl Into<Id>, link: impl Into<Vec2b>) -> Self {
+        self.linked_cursors = Some((group_id.into(), link.into()));
         self
     }