chore: rename master branch to main branch

Author: lepture

.github/workflows/docs.yml

@@ -3,7 +3,7 @@ name: Deploy docs to Pages
 on:
   push:
     branches:
-    - master
+    - main
 
   workflow_dispatch:
 

README.md

@@ -9,7 +9,7 @@ One time password implementations in Python. HOTP and TOTP.
 
 [![Github Actions](https://github.com/authlib/otpauth/actions/workflows/tests.yml/badge.svg)](https://github.com/authlib/otpauth/actions/workflows/tests.yml)
 [![PyPI](https://badgen.net/pypi/v/otpauth)](https://pypi.org/project/otpauth)
-[![codecov](https://codecov.io/gh/authlib/otpauth/branch/master/graph/badge.svg?token=pWQIlZ9Ir4)](https://codecov.io/gh/authlib/otpauth)
+[![codecov](https://codecov.io/gh/authlib/otpauth/branch/main/graph/badge.svg?token=pWQIlZ9Ir4)](https://codecov.io/gh/authlib/otpauth)
 [![Maintainability Rating](https://sonarcloud.io/api/project_badges/measure?project=authlib_otpauth&metric=sqale_rating)](https://sonarcloud.io/summary/new_code?id=authlib_otpauth)
 [![Security Rating](https://sonarcloud.io/api/project_badges/measure?project=authlib_otpauth&metric=security_rating)](https://sonarcloud.io/summary/new_code?id=authlib_otpauth)