Base64 encoder/decoder in Zig

I actually wrote the first version based on the "Introduction to Zig" by Pedro Duarte Faria, but later had to rewrite it, because I moved to the latest stable version of zig, which is currently 0.15.2 and saw that as an opportunity to see if I actually understood stuff, so I rewrote it from scratch. To be honest, I am not proud of writing like a dumb base64, but I wanted to put writing little projects like this in my college application, so I am uploading it here