feat(rest-api-client): add the method of plugin.getApps

[shabaraba]

Why

• Support plugin.getApps method to be able to get the list of Apps that have the specified plug-in added.

What

• Add a document for the new methods.
• Add new unit tests.
• Add type for the new method request and response.

How to test

1. prepare installed plug-ins and add a plug-in to some apps.
2. run below code and check logs:

import {KintoneRestAPIClient} from '@kintone/rest-api-client';

const client = new KintoneRestAPIClient();

const pluginId = (await client.plugin.getPlugins({
  offset: 0,
  limit: 1
})).plugins[0].id;

console.log(await client.plugin.getApps({
  id: pluginId,
}));

Checklist

• Read CONTRIBUTING.md
• Updated documentation if it is required.
• Added tests if it is required.
• Passed pnpm lint and pnpm test on the root directory.