Bevy icon improvements for smaller sizes and "scalability"

[bas-ie]

Bevy icon improvements

PRs #3728 and #4061 have been closed (no activity since 2022). However, their content (SVGs, PNGs) might still be valuable should someone choose to work on our branding images in the future. Briefly summarised, the work of those two PRs was:

• Improve bevy simpleicon for smaller sizes #3728: improve legibility/clarity at smaller sizes
• Improve bevy icons for better "scalability" #4061: adjusts gaps between birds