Provide default export for all schema

[fdarian]

Using schema.ts for drizzle-kit doesn't expose any schema.

export default defineConfig({
  schema: './drizzle/schema/schema.ts',
})

It can't find any tables from the schema.ts, but glob works fine

export default defineConfig({
  schema: './drizzle/schema/*',
})

Originally posted by @hilja in #18 (comment)

[fdarian]

After some thinking, it might be better to just recommend the use of glob pattern instead of introducing another index.ts that re-exports all schema since it'll make IDE to give duplicate recommendations when importing a table. Also barrel file is normally better to be avoided because of (IDE) performance issue

[hilja]

That's great, mentioning it in the docs basically solves the issue. Thank for all the work!