Azurite lacks defaultIndexDocumentPath property of staticWebsite in service properties

**Error Description:**
Azurite doesn't have defaultIndexDocumentPath property of staticWebsite. So defaultIndexDocumentPath is still undefined if set a value for it.

**To Reproduce:**
Please run the demo code as following:
```Typescript
import { BlobServiceClient, StorageSharedKeyCredential } from "@azure/storage-blob";
import { assert } from "chai";

async function main() {
const blobServiceClient = new BlobServiceClient("", new StorageSharedKeyCredential("", ""));
await blobServiceClient.setProperties({
staticWebsite: {
enabled: true,
errorDocument404Path: "error/404.html",
defaultIndexDocumentPath: "index.html"
}
}
);
const staticWebsite = (await blobServiceClient.getProperties()).staticWebsite;
assert.equal(staticWebsite.defaultIndexDocumentPath, "index.html");
}

main();
```

**Error Track:**
[https://github.com/Azure/Azurite/blob/master/src/blob/generated/artifacts/mappers.ts#L1376](https://github.com/Azure/Azurite/blob/master/src/blob/generated/artifacts/mappers.ts#L1376)
It can be seen from this picture that Azurite lacks `defaultIndexDocumentPath` property of `staticWebsite`.

**Expected Behavior:**
Add the `defaultIndexDocumentPath` property into `staticWebsite` in Azurite.

@jongio for notification.