Release v0.3.8: VS Code Extension Icon

This release adds a professional icon for the VS Code extension, improving
visual identity and marketplace presence.

Major Changes:
- Added 128x128 PNG icon for VS Code extension
- Icon design features processor chip with instruction format visualization
- Blue gradient theme representing ISA/processor architecture
- Includes SVG source file for future modifications

Features:
- Professional icon design suitable for programming language extension
- Icon configured in package.json for automatic marketplace display
- Modern, tech-focused visual identity
- "0xISA" hexadecimal indicator for brand recognition

Implementation:
- Created icon.svg (source file, 2.5KB)
- Generated icon.png (128x128 PNG, 5.7KB)
- Updated package.json with icon field
- Icon appears in VS Code Extensions view and marketplace

Documentation:
- Updated RELEASE_NOTES.md with version 0.3.8 details
- Updated version badges in README.md and extension README.md

Test Results:
- 193 Python tests passing
- 55 VS Code extension tests passing
- All tests passing, 0 skipped, 0 failed

Version Updates:
- pyproject.toml: 0.3.7 → 0.3.8
- vscode_extension/isa/package.json: 0.3.7 → 0.3.8
- vscode_extension/isa/packages/extension/package.json: 0.3.7 → 0.3.8
- vscode_extension/isa/packages/language/package.json: 0.3.7 → 0.3.8

Files Changed:
- New: vscode_extension/isa/packages/extension/icon.png
- New: vscode_extension/isa/packages/extension/icon.svg
- Modified: vscode_extension/isa/packages/extension/package.json (added icon field)
- Modified: RELEASE_NOTES.md (added v0.3.8 entry)
- Modified: README.md (version badge)
- Modified: vscode_extension/isa/packages/extension/README.md (version badge)
- Modified: All package.json files (version bump)
