Adding Gallery CTAs
Merge branch 'overlay' into fullscreen-galleries

Conflicts:
	common/app/assets/images/global/sprite.png
	common/app/assets/stylesheets/theme/_global-icons-sprite.scss
Adding Gallery CTAs
Adding basic styles
Adding temporary lightbox gallery template
Aspect Ratioed containers should hide the overflow
Adding JS
Filename typo
Adding caption toggle
Hiding nav arrows in Grid mode
Updated overlay colour
Updated caption background
Merge branch 'overlay' into fullscreen-galleries

Conflicts:
	common/app/assets/stylesheets/module/_overlay.scss
Adding tests
Unnecessary classname
Updated gallery arrow CTA
Improved Overlay display method (less jankiness)
Faster taps
Merge branch 'fullscreen-galleries' of github.com:guardian/frontend into fullscreen-galleries
Fixes the scroll position not being restored