chore: split kpms into separate optional dependencies for CPU and GPU, update README

[MilagrosMarin]

No description provided.

[Copilot]

Pull Request Overview

This PR reorganizes optional dependencies by separating CPU and GPU variants for keypoint-moseq (kpms) and adds installation instructions with conda environment setup.

• Splits kpms dependency into separate kpms_cpu and kpms_gpu options to support different hardware configurations
• Adds new deeplabcut and all optional dependency groups for better package organization
• Updates README with conda environment setup instructions and revised pip installation command

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
pyproject.toml	Restructures optional dependencies with separate CPU/GPU kpms variants and adds deeplabcut/all groups
README.md	Adds conda environment setup steps and updates pip installation to use new kpms_cpu dependency

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