Add initial project structure and core functionality for ArchDoc

- Created `.gitignore` files for various directories to exclude unnecessary files.
- Added `PLAN.md` to outline the project goals and architecture documentation generation.
- Implemented the `archdoc-cli` with a command-line interface for initializing and generating documentation.
- Developed the `archdoc-core` library for analyzing Python projects and generating architecture documentation.
- Included caching mechanisms to optimize repeated analysis.
- Established a comprehensive test suite to ensure functionality and error handling.
- Updated `README.md` to provide an overview and installation instructions for ArchDoc.

test-project/README.md

@@ -0,0 +1,22 @@
+# Test Project
+
+A test project for ArchDoc development and testing.
+
+## Installation
+
+```bash
+pip install -e .
+```
+
+## Usage
+
+```bash
+test-project
+```
+
+## Development
+
+Install development dependencies:
+
+```bash
+pip install -e ".[dev]"