Image modal fixes

[xvandish]

expand btn fit within container, constrain tall images to viewport height, attatch click handler to expand btn

Description of Change

This knocks out 3 bugs.

1. Constrains expand button to within image.
2. Constrains tall images to viewport height, so the entire image is visible
3. Attaches click handler to the expand button (worked before because clicks propagated to image, except in the case where the expand button was outside of the image)

Related Issue

#290 #297

Motivation and Context

Checklist

• Ran npm run lint and updated code style accordingly
• npm run test passes
• PR has a description and all contributors/stakeholder are noted/cc'ed
• tests are updated and/or added to cover new code
• relevant documentation is changed and/or added

[xvandish]

For a future PR, I have a partially working idea for scaling the expand button based on the size of the image, in case an image smaller than the current dimensions (60x60) is displayed -

[afischer]

Thanks for the fixes, looks great!