fix(buffer): scroll to selection on buffer open

We already set the selection based on the neovim cursor from the
external buffer, but we should also scroll so that it's visible. This might
be better fixed with proper syncing like vscode-neovim#1261 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);