Fix badge in readme

Author: Xennis

README.md

@@ -1,6 +1,6 @@
 # EpiDoc Parser
 
-[![Python](https://github.com/Xennis/epidoc-parser/actions/workflows/python.yml/badge.svg?branch=master&event=push)](https://github.com/Xennis/epidoc-parser/actions/workflows/python.yml?query=event%3Apush+branch%3Amaster)
+[![Python](https://github.com/Xennis/epidoc-parser/actions/workflows/python.yml/badge.svg?branch=main&event=push)](https://github.com/Xennis/epidoc-parser/actions/workflows/python.yml?query=event%3Apush+branch%3Amain)
 
 Python parser for EpiDoc (epigraphic documents in TEI XML).