Add Full Screen Image Overlay Option

[paulpwo]

I recently discovered this repository, but when implementing it, I needed my Bitmap to fit 100% of the height and width of the video (very useful for working with layers of processes, where I insert text enriched with emojis, capture them as an image and insert them into the video). I searched for several ways from Flutter, but since I was not successful, I made some modifications. I created a GlImageOverlayFilterFull on Android and I am working on getting the same result on IOS.

If you would like to add this feature, just let me know and I will create a pull request.