Feature Request: Official Zig language support for FlatBuffers code generation

## Summary

Please add official Zig language support to the `flatc` code generator.

## Background

[Zig](https://ziglang.org/) is a systems programming language with growing adoption in the
native/embedded/performance-sensitive ecosystem. It compiles to native code, has no hidden
control flow, and interoperates directly with C ABI — making it a natural fit for FlatBuffers.

We are currently building [zarrow](https://github.com/tylitianrui/zarrow), a Zig
implementation of Apache Arrow that depends on FlatBuffers for its IPC wire format. Right now
we rely on a third-party wrapper ([flatbufferz](https://github.com/archaistvolts/flatbufferz))
to consume the generated code, because there is no official `flatc --zig` backend.

## What we are asking for

- A `--zig` backend in `flatc` that generates idiomatic Zig structs/unions for FlatBuffers
schemas.
- Generated code should target the current stable Zig release (0.15.x) and track breaking
language changes going forward.

## Why now

- Zig 0.14+ has a stable package manager (`build.zig.zon`), making it practical to distribute
a generated runtime as a dependency.
- Several projects (Arrow, TensorFlow Lite, game engines) already target Zig, creating demand
for first-class schema-based serialization support.

## References

- Zig language: https://ziglang.org/
- Existing community wrapper: https://github.com/archaistvolts/flatbufferz
- FlatBuffers language support tracking: https://google.github.io/flatbuffers/flatbuffers_support.html