Add ziggy language extension

[lvignoli]

Ziggy support for Zed.

The LSP cannot be installed because of an upstream issue: releases for ziggy are distributed as tar.xz, not tar.gz.
As I understand, Zed extension SDK does not support this compression format.

Linked issues:

• XZ Utils decompression support for Extension downloads zed#21407
• Use tar.gz for releases? kristoff-it/ziggy#48

[notpeter]

If we know that the download/extraction will fail, can we:

1. comment out that code
2. require users to manually download and install ziggy into their PATH
3. output an error when which fails to find the ziggy binary?

[lvignoli]

@notpeter indeed, that's much sounder. Is this the proper way to do so?

[notpeter]

Thanks!