More documentation with samples in typescript

There's this [walkthrough](https://docs.aws.amazon.com/cloudformation-cli/latest/userguide/resource-type-walkthrough.html) but it's using *java* as the language, and it's not very easy to understand.

From the documentation perspective, I don't understand how to call `dynamodb` from the handlers for example. It looks like I need to use the `SessionProxy`, but it's not documented how to get a hold of *dynamodb* aws client.
In the *init* example:
```
// Example:
try {
if (session instanceof SessionProxy) {
const client = session.client('S3');
}
```
1. Where's the documentation of which *string* should I pass in the `.client([string])` to get dynamodb, stepfunction (or others) clients?

2. Even after I run `npm install` to install the dependencies, VSCode still does not find `@amazon-web-services-cloudformation/cloudformation-cli-typescript-lib`


3. Also, do I need to implement all "create, update, list, read..." operations? I was looking for to implement only *create*, *update* and *delete*.

审查链接的 AWS CloudFormation 资源类型指南以及使用 SessionProxy 的 TypeScript init 示例。验证 DynamoDB 等服务客户端的命名和获取方式、VSCode 找不到已安装的 TypeScript 库的原因，以及需要哪些 handler；完成的标准是该指南通过可运行的示例回答这些问题。

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