feat(rest-api-client): add plugin.getPlugins, getRequiredPlugins, and getApps

[shabaraba]

Why

• Support plugin.getPlugins method to be able to get the list of plug-ins imported into Kintone.
• Support plugin.getRequiredPlugins method to be able to get the list of plug-ins that have been deleted from Kintone, but have already been added to Apps.
• Support plugin.getApps method to be able to get the list of Apps that have the specified plug-in added. (#2900)

What

• Add a document for the new methods.
• Add new unit tests.
• Add type for Plugin

NOTE: This PR also includes plugin.getApps (#2900)

How to test

1. prepare installed plug-ins and required plug-ins in Kintone.
2. run below code and check logs:

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

const client = new KintoneRestAPIClient();

console.log(await client.plugin.getPlugins({
  offset: 0,
  limit: 2
}));

console.log(await client.plugin.getRequiredPlugins({
  offset: 0,
  limit: 2
}));

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.

[tasshi-me]

レビュー2箇所追加しました！
確認お願いします！

[tasshi-me]

LGTM！