Add Windows installation instructions to README

Windows users currently have no clear installation instructions in the README. The existing Linux/macOS instructions don't directly translate, causing confusion for contributors on Windows.

Add a dedicated Windows installation section to the README with step-by-step instructions, similar to the existing Linux/macOS sections.

**Suggested Windows Installation Steps:**

```
install Git for Windows (includes Git LFS): https://git-scm.com/download/win
git lfs install
git clone [git@github.com](mailto:git@github.com):apple/corenet.git
cd corenet
git lfs pull

```

Create virtual environment
python -m venv venv
venv\Scripts\activate

Install CoreNet
`pip install --editable .`

Optional: Audio/Video dependencies
Install FFmpeg via Chocolatey: choco install ffmpeg
Or download from: https://ffmpeg.org/download.html
text

**Additional context**
- Requires Python 3.10+ and PyTorch >=2.1.0 (same as Linux)
- Windows users should use Git Bash, PowerShell, or Command Prompt
- FFmpeg installation options: Chocolatey, Scoop, or direct download
- Consider adding note about case sensitivity differences vs macOS

**Benefits**
- Enables Windows contributors (significant portion of ML community)
- Reduces support burden on maintainers
- Makes CoreNet more accessible across all major platforms

**Alternative**
Happy to submit a PR with these changes if maintainers prefer that approach!

**Environment**
- OS: Windows 10/11
- Python: 3.10+
- PyTorch: >=2.1.0

Open the README and compare the existing Linux/macOS installation sections with the proposed Windows steps. Add a dedicated Windows section covering Git LFS, the virtual environment, editable installation, and optional FFmpeg setup, then verify that the Python 3.10+ and PyTorch requirements remain consistent.

Written by the indexing model from the issue text.