The "In-depth Overview" still uses `zig init-exe` insetad of `zig init`

[AlexanderHott]

From #335 and #323 it looks like the zig init-exe command moved to zig init, but the "Zig Build System" section in the "In-depth Overview" still uses zig init-exe.

I think the relevant line is here https://github.com/ziglang/www.ziglang.org/blob/main/content/en-US/learn/overview.smd#L427, however the documentation doesn't describe all the generated files from zig init (like build.zig.zon). I'm guessing this page needs a refresh after some of the updates to zig.