allow passing api key as env var (#841)

Allow passing API key as env var:
```shell
export LANCEDB_API_KEY=sh_123...
```

with this set, apiKey argument can omitted from `connect`
```js
    const db = await vectordb.connect({
        uri: "db://test-proj-01-ae8343",
        region: "us-east-1",
  })
```
```py
    db = lancedb.connect(
        uri="db://test-proj-01-ae8343",
        region="us-east-1",
    )
```

node/src/index.ts

@@ -78,7 +78,11 @@ export interface ConnectionOptions {
   /** AWS region to connect to. Default is {@link defaultAwsRegion}. */
   awsRegion?: string
 
-  // API key for the remote connections
+  /**
+   * API key for the remote connections
+   *
+   * Can also be passed by setting environment variable `LANCEDB_API_KEY`
+   */
   apiKey?: string
 
   /** Region to connect */