Add comprehensive README documentation

- Project overview and features
- Installation and usage instructions
- Detailed explanation of how hardlink-based backups work
- Command-line options and examples
- Backup structure and retention policy details
- Development and testing information

.github/workflows/run_tests.yml

@@ -9,9 +9,9 @@ jobs:
       matrix:
         python-version: ["3.6", "3.7", "3.8", "3.9", "3.10", "3.11"]
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v4
     - name: Set up Python ${{ matrix.python-version }}
-      uses: actions/setup-python@v2
+      uses: actions/setup-python@v4
       with:
         python-version: ${{ matrix.python-version }}
     - name: Install dependencies