inconsistent use of language selector icon & other SVG asset problems

I just took a peek at how the language picker icon is implemented on this site and strangely found it amongst the HTML+Liquid in _layouts/menu.html while all the other SVG assets are located in the assets/img directory. The files located in that directory also have problems. For example, the menu-down.svg icon strangely includes a line indicating that Apple owns the copyright to it (view source).

I also discovered that several other optimizations could significantly reduce the size of all these SVGs. Compare this to a manually optimized one i made a while ago for some other project: https://codepen.io/DerekNonGeneric/pen/bGroexG.

We can even take this a step further by minifying the assets and can probably make additional corrections in the process (viewbox of TC39 logo seems off) and we should probably ensure all are following a11y best practices (accessible SVGs).

Start with _layouts/menu.html and compare its language picker icon with the SVGs in assets/img. Inspect menu-down.svg and logo.svg for the reported copyright, optimization, viewBox, and accessibility concerns, then review the remaining assets for similar problems. Done means the icons are consistently organized and corrected without losing their intended appearance or accessibility.