Scroll to selection when opening external buffer

We already set the selection based on the neovim cursor, but we should
also scroll so that it's visible. This might be better fixed by
something like vscode-neovim#993 but for now it makes :help work a lot nicer.

src/buffer_manager.ts

@@ -805,7 +805,10 @@ export class BufferManager implements Disposable, NeovimRedrawProcessable, Neovi
                     } catch (e) {
                         this.logger.warn(`${LOG_PREFIX}: Unable to get cursor pos for external buffer: ${id}`);
                     }
-                    editor.selections = [new Selection(finalLine, finalCol, finalLine, finalCol)];
+
+                    const selection = new Selection(finalLine, finalCol, finalLine, finalCol);
+                    editor.selections = [selection];
+                    editor.revealRange(selection, TextEditorRevealType.AtTop);
                 }
             }, 1000);