Icons assets as svg

[clxandstuff]

After this change, we don't need to include icons JS scripts to use icons components: Icon, MathSymbol, SubjectIcon, MobileIcon. It should also unblock main thread when loading icons leading to better page performance.

Icon components use new strategy to retrieve icon from sprite, from:

<svg>
  <use xlink:href="#icon-academic_cap" />
</svg>

to

<svg>
  <use href="https://style-guide.brainly.com/images/svg-sprites/icons-tg6372uy1.svg#icon-academic_cap" />
</svg>