Add information about publishing

README.md

@@ -60,6 +60,13 @@ To install this gem onto your local machine, run `bundle exec rake install`. To
 
 Bug reports and pull requests are welcome on GitHub at https://github.com/qoqa/swiss_bank_validator. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the [code of conduct](https://github.com/qoqa/swiss_bank_validator/blob/master/CODE_OF_CONDUCT.md).
 
+## Publishing
+
+To publish a new version, you need to:
+- Bump the version in `lib/swiss_bank_validator/version.rb`
+- Create a new version on Github
+- Run `gem build swiss_bank_validator`
+- Run `gem push swiss_bank_validator-<version>.gem`
 
 ## License