[DOCS]: Add config parameter example for `migrate` function

Several docs currently show `migrate(db)` without the required config parameter, which can confuse developers. As of now, the `migrate` function needs a config object, for example:

```ts
await migrate(db, { migrationsFolder: './drizzle' })
```

The option is missing in main docs such as:
- [`src/content/docs/migrations.mdx`](https://github.com/drizzle-team/drizzle-orm-docs/blob/main/src/content/docs/migrations.mdx)

Please update the relevant sections to include the config usage and make it clear this parameter is necessary.

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*Submitted with the assistance of AI.*