Add stamp tool, fix centering of default shapes created by click

[#76530828]
[#78193090]
Add text buttons and spin animation (CSS, stamp tool)

[#76530828]
Fix palettes positioning, support 'hideOnClick' option

[#76530828]
Make sure that locked buttons don't call their handlers on click

[#76530828]
Support dynamic generation of stamps

[#76530828]
Improve image button styling

[#76530828]
Add example page with stamps

[#76530828]