Add compute_workgroups example

[mrinalchaturvedi27]

This PR adds a compute_workgroups.py example demonstrating GPU workgroups and invocation IDs.
While reviewing the WGPU documentation and the Rust hello_workgroups example, I noticed that wgpu-py does not include a focused example for workgroups.
This example provides a minimal compute shader that writes global_invocation_id, local_invocation_id, and workgroup_id into a storage buffer so the relationship between them can be inspected.

[Copilot]

Pull request overview

Adds a new compute_workgroups.py example to the examples/ suite to help users understand how compute workgroups relate to invocation IDs in wgpu-py, by writing invocation/workgroup identifiers into a storage buffer and printing/verifying the mapping on the CPU.

Changes:

• Add a minimal WGSL compute shader that records global_invocation_id, local_invocation_id, and workgroup_id (currently x-components) into a storage buffer.
• Add a Python driver that dispatches workgroups, reads back the buffer, prints a table, and validates the expected ID relationships.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[mrinalchaturvedi27]

Hi @Korijn @almarklein, just checking in on this PR. Whenever you get a chance, could you please take a look? Happy to make any changes if needed. Thanks!

[almarklein]

LGTM, thanks!