Add additional shapes/images at meme creation

Allow to place shapes somehwere in the image, e.g. a hat somewhere. This should be moveable until user accepts. After accepting the hat will be drawn to a copy of the original edit image. The hat should be still there if e.g. the text or a font is changed (image redrawn). The shape also needs to be scaleable (edges) This may share it's codebase with #46.

Show e.g. a list of shapes:

Add a moveable shape to the image:

Start by reviewing the meme-creation flow and the related requirements in issue #46. Done means users can choose a shape or image, move and scale it before accepting, and the accepted overlay remains when text or fonts cause the image to be redrawn.

Written by the indexing model from the issue text.