message: [terminal_renderer] Adding many more symbols for explicit rendering.
diff: namespace terminal::renderer {
  +// TODO(pr) I think I should cincerely rename this class to
  +// something more suitable. it's not about box-drawing alone anymore,
  +// but about manually rendering anything that needs to properly fit
  +// into the grid cell.
  +// - box drawing symbols
  +// - symbols for legacy computing
  +// - mathematical symbols
  +
  /// Takes care of rendering the text cursor.
  class BoxDrawingRenderer : public Renderable {
  public:
  