feat: many to many relations

[0xcadams]

Added many to many relations through a junction table:

export const schema = createSchema(
  createZeroSchema(drizzleSchema, {
    version: 1,
    tables: {
      user: {
        id: true,
        name: true,
      },
      group: {
        id: true,
        name: true,
      },
      users_to_group: {
        user_id: true,
        group_id: true,
      },
    },
    manyToMany: {
      // The origin table to define the many-to-many relationship on
      user: {
        // The key is the relation name and value is [junction table, target table]
        groups: ["users_to_group", "group"],
      },
    },
  }),
);