Bring back the code documentation

[orhun]

Is your feature request related to a problem? Please describe.

zig build -Ddocs=true used to create a folder called docs and it contained the documentation. This does not work anymore.

Describe the solution you'd like

Look into what's wrong and bring that back!

Describe alternatives you've considered

None.

Additional context

Some things have changed apparently...

[alexmgullen]

Alright, using zig 0.12.0 on Debian 12 and Windows 11, I could get the docs output to zig-out/docs. I'm thinking an API change caused addInstallDirectory() to stop writing to the root by default and instead write to zig-out.