Update import examples in README (#167)

## Problem

The import examples in the README are missing some class imports.

## Solution

Add the imports.

## Type of Change

- [ ] Bug fix (non-breaking change which fixes an issue)
- [ ] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to not work as expected)
- [ ] This change requires a documentation update
- [ ] Infrastructure change (CI configs, etc)
- [x] Non-code change (docs, etc)
- [ ] None of the above: (explain here)

## Test Plan

Describe specific steps for validating this change.

README.md

@@ -658,6 +658,8 @@ System.out.println(result.getData());
 The following example initiates an asynchronous import of vectors from object storage into the index.
 
 ```java
+import io.pinecone.clients.Pinecone;
+import io.pinecone.clients.AsyncIndex;
 import org.openapitools.db_data.client.ApiException;
 import org.openapitools.db_data.client.model.ImportErrorMode;
 import org.openapitools.db_data.client.model.StartImportResponse;
@@ -680,6 +682,8 @@ StartImportResponse response = asyncIndex.startImport(uri, "123-456-789", Import
 The following example lists all recent and ongoing import operations for the specified index.
 
 ```java
+import io.pinecone.clients.Pinecone;
+import io.pinecone.clients.AsyncIndex;
 import org.openapitools.db_data.client.ApiException;
 import org.openapitools.db_data.client.model.ListImportsResponse;
 ...
@@ -698,6 +702,8 @@ ListImportsResponse response = asyncIndex.listImports(100, "some-pagination-toke
 The following example retrieves detailed information about a specific import operation using its unique identifier.
 
 ```java
+import io.pinecone.clients.Pinecone;
+import io.pinecone.clients.AsyncIndex;
 import org.openapitools.db_data.client.ApiException;
 import org.openapitools.db_data.client.model.ImportModel;
 ...
@@ -716,6 +722,8 @@ ImportModel importDetails = asyncIndex.describeImport("1");
 The following example attempts to cancel an ongoing import operation using its unique identifier.
 
 ```java
+import io.pinecone.clients.Pinecone;
+import io.pinecone.clients.AsyncIndex;
 import org.openapitools.db_data.client.ApiException;
 ...