A simple Open edX XBlock to display images with captions and long descriptions.
Template 1 is designed for full-width images, template 2 causes the image to take 70% of the width, leaving the remaining space for the caption. For responsive themes, template 2 will go full width when below a certain threshold (currently based off the Appsembler-OU theme, you may need to adjust the threshold for your own instance).
Alt text is set by default to direct users to the long description, so for images to be accessible a long description is required.
Name for enabling in Studio: 'captionedimage'
