doc: add usage and installation to README

Author: corneliusroemer

README.md

@@ -1,5 +1,41 @@
 [![Python package](https://github.com/corneliusroemer/pango_aliasor/actions/workflows/pytest.yaml/badge.svg)](https://github.com/corneliusroemer/pango_aliasor/actions/workflows/pytest.yaml)
 
+Python convenience library to translate between aliased and unaliased Pango lineages
+
+Useful for:
+- constructing a tree of Pango lineages
+- semantic sorting of Pango lineages
+- ...
+
+## Usage
+
+```python
+from pango_aliasor.aliasor import Aliasor
+
+# Initalize aliasor (only needs to be done once)
+# If no alias_key.json is passed, downloads the latest version from github
+aliasor = Aliasor()
+
+# To use custom alias_key.json, pass the relative path to the file
+# aliasor = Aliasor('alias_key.json')
+
+# Go from aliased lineage to unaliased lineage
+aliasor.uncompress("BA.5") # 'B.1.1.529.5'
+aliasor.uncompress("BE.5") # 'B.1.1.529.5.3.1.5'
+aliasor.uncompress("XA") # 'XA'
+
+# Go from unaliased lineage to aliased lineage
+aliasor.compress("B.1.1.529.3.1") # 'BA.3.1'
+```
+
+See [tests](tests/test_aliasor.py) for more examples.
+
+## Installation
+
+```bash
+pip install pango_aliasor
+```
+
 ## Testing
 
 Run `pytest` from the project root to run all tests.