blabber

I have a liberal licensed and attributed svg icon in my local. Will push a PR after testing.

These icons don't seem adapt to dark and light mode (it's always white on black), but I made sure to mimic the other svg icons.

Without this PR:  With this PR: 

> @blabber would you pls upload the save game you have w/ fallout? 🫴 [fallout.sav.xz.zip](https://github.com/longturn/freeciv21/files/14954576/fallout.sav.xz.zip)

> You need to add `fill="#000"` to the top level `

On Discord at least one voice was cast against these changes: https://discord.com/channels/378908274113904641/857286127165112370/1225396755789512715 In the previous PR, there was still a discussion about whether casus belli still had to be handled...

Slightly OT, but as I use Tweetian daily, I am also interested in supporting further development with donations if you provide a way to do so.