Add sb-osc to README

[jjh-kim]

Description

We recently released a new online schema change tool sb-osc as an open source. It uses python-mysql-replication for capturing DML events from database, so we'd like to add this to the list in README
cc. @dongwook-chan

Type of Change

• Bug fix
• New feature
• Documentation update
• Other (please specify below)

Checklist

• I have read and understood the CONTRIBUTING.md document.
• I have checked there aren't any other open Pull Requests for the desired changes.
• This PR resolves an issue #[Issue Number Here].

Tests

• All tests have passed.
• New tests have been added to cover the changes. (describe below if applicable).

Additional Information

SB-OSC blog

[julien-duponchelle]

Thank you so much !