[DRAFT] feat: add a bullet image

[alasdairmackenzie]

Hey, this is a draft PR for https://github.com/gitbrent/PptxGenJS/issues/898

Hoping to get some feedback if possible -

My main issue that the image is added to the slide at x:0 and y:0 rather than hiding it. I'm not sure this is the best way to go. What are your thoughts on modifying the addImageDefinition function to create a 'hidden' image? Do you have another suggestion?

It's be great to hear your thoughts

(Ignore the changes to index.html and the typescript hack for now)

[gitbrent]

Hi Alasdair,

Are you saying that PowerPoint is showing the image at (0,0) in addition to being the bullet itself?