chore: correct export style

Author: achingbrain

src/index.js

@@ -1,12 +1,21 @@
+import * as ErrorsImport from './errors.js'
+import * as ShardImport from './shard.js'
+
 export { BaseDatastore } from './base.js'
 export { MemoryDatastore } from './memory.js'
 export { KeyTransformDatastore } from './keytransform.js'
 export { ShardingDatastore } from './sharding.js'
 export { MountDatastore } from './mount.js'
 export { TieredDatastore } from './tiered.js'
 export { NamespaceDatastore } from './namespace.js'
-export * as Errors from './errors.js'
-export * as shard from './shard.js'
+
+export const Errors = {
+  ...ErrorsImport
+}
+
+export const shard = {
+  ...ShardImport
+}
 
 /**
  * @typedef {import("./types").Shard } Shard