Add professional project structure and documentation

New files:
- LICENSE (MIT) - Required legal file
- CHANGELOG.md - Version history following Keep a Changelog
- CONTRIBUTING.md - Contributor guidelines
- CODE_OF_CONDUCT.md - Community standards
- .github/ISSUE_TEMPLATE/ - Bug report and feature request forms
- .github/PULL_REQUEST_TEMPLATE.md - PR checklist
- src/stegasoo/py.typed - PEP 561 type hint marker
- examples/ - Usage examples (basic, file embedding, channel keys)

Updated:
- README.md - Added CI status badges

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

examples/README.md

@@ -0,0 +1,48 @@
+# Stegasoo Examples
+
+This directory contains example scripts demonstrating how to use Stegasoo.
+
+## Prerequisites
+
+Install Stegasoo first:
+
+```bash
+pip install stegasoo
+# Or for development:
+pip install -e ".[all]"
+```
+
+## Examples
+
+### basic_usage.py
+
+Basic encode/decode workflow with a text message.
+
+```bash
+python basic_usage.py
+```
+
+### embed_file.py
+
+Embed and extract files (documents, images, etc.) inside carrier images.
+
+```bash
+python embed_file.py
+```
+
+### channel_keys.py
+
+Use channel keys to create private communication channels for groups.
+
+```bash
+python channel_keys.py
+```
+
+## Test Images
+
+You'll need to provide your own images:
+
+- `my_secret_photo.png` - Your reference photo (keep this secret!)
+- `carrier.png` - The image that will carry your hidden message
+
+For testing, you can use any PNG or BMP image. JPEG carriers are supported with DCT mode.