mention to TypeScript prerequisites

README.md

@@ -60,6 +60,7 @@ deepStrictEqual(decode(encoded), object);
 - [Prerequsites](#prerequsites)
   - [ECMA-262](#ecma-262)
   - [NodeJS](#nodejs)
+  - [TypeScript](#typescript)
 - [Benchmark](#benchmark)
 - [Distribution](#distribution)
   - [NPM / npmjs.com](#npm--npmjscom)
@@ -485,6 +486,12 @@ NodeJS v10 is required, but NodeJS v12 or later is recommended because it includ
 
 NodeJS before v10 will work by importing `@msgpack/msgpack/dist.es5/msgpack`.
 
+### TypeScript
+
+This module requires definitions of `AsyncIterator` and whatwg streams, which is specified with `"lib": ["ES2020", "DOM"]` in `tsconfig.json`.
+
+For the TypeScript version, the latest TypeScript is tested in development, but older versions of TypeScript might be able to compile this module.
+
 ## Benchmark
 
 Run-time performance is not the only reason to use MessagePack, but it's important to choose MessagePack libraries, so a benchmark suite is provided to monitor the performance of this library.