Speed optimisations

[AlexTr]

• When custom icons are used (especially SVG) like on UNA.io, we need to somehow pre-load them asynchronously to make sure that first access to non-cached menus doesn't take too long. Currently first loading takes 3-5 seconds and appears sluggish.

• Address, where possible, all blocking JS and CSS loads. Detailed here - https://developers.google.com/speed/pagespeed/insights/ & https://web.dev/measure/

• Address slow server response and make sure out setup isn't an issue. It's 0.59 seconds and makes a noticeable delay. https://developers.google.com/speed/pagespeed/insights/?url=una.io&tab=desktop.

• Setup browser caching and JS, CSS, HTML magnification. Perhaps a UNA app like "Speed" with settings for various optimisation tools would be best. This would allow us to update it periodically and separate any optimisations that may potentially cause issues. Even things like AMP could be added to it eventually.