Add polyglot-hooks to EXPERIMENTS.md

[moskyb]

We missed adding this in the original PR, whoops.

polyglot-hooks

Allows the agent to run hooks written in languages other than bash. This enables the agent to run hooks written in any language, as long as the language has a runtime available on the agent. In non-windows environments, polyglot hooks can be in interpreted languages, so long as they have a valid shebang, and the interpreter specified in the shebang is installed on the agent.

This experiment also allows the agent to run compiled binaries (such as those produced by Go, Rust, Zig, C et al.) as hooks, so long as they are executable.

Hooks are run in a subshell, so they can't modify the environment of the agent process. However, they can use the job-api to modify the environment of the job.

Status: Experimental while we try to cover the various corner cases. We'll probably promote this to non-experiment soon™️.

[DrJosh9000]

Looks good! 🌿