Check writing of all posts in edition 2

[hecatia-elegua]

This fixes grammar, punctuation, etc. and clarifies some sentences.

I'm keeping this as a draft for now, but I want to help out a lot more. If you want, I can also split every writing check into its own PR, but I'm trying to stay conservative with the changes. I'm using my common sense and, in some places, grammar checkers.

[phil-opp]

Thanks a lot for this effort! The changes look all good to me.

It sounds like you're planning to add more commits? Just let me know when this is ready to be merged.

[hecatia-elegua]

This is ready now :)

02, 10, 11, and 12 have some more info in their commit messages about where I changed some outdated stuff.

[phil-opp]

Thanks a lot for all your work! I'm still reviewing your changes, but what I've seen so far looks very good.

[hecatia-elegua]

Thank you for this amazing project!