message: Update README.md
  minor typo regarding alignment of an object
diff: @@ -146,7 +146,7 @@ let slide = pres.addSlide();
  // 3. Add one or more objects (Tables, Shapes, Images, Text and Media) to the Slide
  let textboxText = "Hello World from PptxGenJS!";
  -let textboxOpts = { x: 1, y: 1, color: "363636", fill: "f1f1f1", align: pptx.AlignH.center };
  +let textboxOpts = { x: 1, y: 1, color: "363636", fill: "f1f1f1", pres: pptx.AlignH.center };
  slide.addText(textboxText, textboxOpts);
  // 4. Save the Presentation
  