docs/migrations: add Atlas/Sequelize integration

[a8m]

Hey team,

Atlas is a Schema-as-Code and migration tool that supports most ORMs. A few months ago, we added support for Sequelize after it was requested many times by our community. In short, what Atlas provides for Sequelize' users is:

• Automatic migration planning: It can read the Sequelize models from either JS/TS definitions and maintains for the users the migrations directory. Your can see the provider on GitHub: ariga/atlas-provider-sequelize
• Schema diff: Atlas can compare Sequelize schema to databases, other Sequelize projects or other ORMs.
• Allow extending the Sequelize schema with additional non ORM-ish objects such as triggers, RLS, functions, etc.
• Migration linting, testing, and more.

For other example integrations we did:

• Prisma: https://www.prisma.io/blog/advanced-database-schema-management-with-atlas-and-prisma-orm
• GORM: https://gorm.io/docs/migration.html#Atlas-Integration
• Ent: https://entgo.io/docs/versioned-migrations
• Beego, and more here: https://atlasgo.io/orms

[a8m]

Hey @WikiRik, just a quick reminder on this. Let me know if you need anything from me. Thanks!