Add `helm` extension to Zed editor

[cabrinha]

Zed is a new editor that looks fun to use, but currently does not support Helm syntax.

Perhaps we can get it working via their extensions: https://github.com/zed-industries/extensions

I tried and failed here: https://github.com/zed-industries/extensions/pull/443

Here is my helm.zed repo, but I'm not sure its correctly setup: https://github.com/cabrinha/helm.zed

Especially the injections.scm file.