Downgrade holder.js to v2.2.0.

Fixes #12440.
Merge pull request #12463 from XhmikosR/12440

Downgrade holder.js to v2.2.0.
Docs: losslessly compress images.

docs/assets/img/components.png | Bin 3201 -> 3196 bytes
docs/assets/img/devices.png    | Bin 6661 -> 6655 bytes
docs/assets/img/sass-less.png  | Bin 15911 -> 14588 bytes