Add instructions for taking good screenshots for release notes

[alice-i-cecile]

Discussed starting here.

I still spent a lot of time capturing / recording media, either because it wasn't included, it didn't follow conventions (the big ones being including "debug text" and "OS window decorations"), or it didn't put the feature in its best light. I also spent a reasonable amount of time re-encoding / trimming (converting pngs to jpgs to cut down size, cutting down videos that were too long / weren't mp4s / were "too big", etc)

It's too hard for me to do. Idk how to take screenshots without the window title, add the text, etc

Probably just need to have a template for setting the window size, setting it to borderless, displaying some text with a certain font, etc

it would be cool if there was some command-line config for examples that removed the window titles, etc. I've spent some time doing similar things and we might be able to plop an example plugin with the config behind a flag?

We could also maybe use the bevy_cli project for this?