docs: localize README with Simplified and Traditional Chinese translations

- Add links to Traditional and Simplified Chinese README files, and label English as the default language
- Fix formatting for the list of supported platforms in the main README
- Add a Simplified Chinese version of the README with equivalent content and instructions
- Add a Traditional Chinese version of the README with equivalent content and instructions

Signed-off-by: appleboy <appleboy.tw@gmail.com>

README.md

@@ -1,5 +1,7 @@
 # drone-ssh
 
+> **English** | [繁體中文](./README.zh-tw.md) | [简体中文](./README.zh-cn.md)
+
 ![sshlog](images/ssh.png)
 
 [![GitHub tag](https://img.shields.io/github/tag/appleboy/drone-ssh.svg)](https://github.com/appleboy/drone-ssh/releases)
@@ -42,9 +44,9 @@ pipeline:
 
 The pre-compiled binaries can be downloaded from [release page](https://github.com/appleboy/drone-ssh/releases). Support the following OS type.
 
-* Windows amd64/386
-* Linux arm/amd64/386
-* Darwin amd64/386
+- Windows amd64/386
+- Linux arm/amd64/386
+- Darwin amd64/386
 
 With `Go` installed
 
@@ -117,7 +119,7 @@ See [DOCS.md](./DOCS.md) for examples and full configuration options
 
 Configuration options are loaded from multiple sources:
 
-0. Hardcoded drone-ssh defaults.  See [main.go CLI Flags](https://github.com/appleboy/drone-ssh/blob/6d9d6acc6aef1f9166118c6ba8bd214d3a582bdb/main.go#L39) for more information.
+0. Hardcoded drone-ssh defaults. See [main.go CLI Flags](https://github.com/appleboy/drone-ssh/blob/6d9d6acc6aef1f9166118c6ba8bd214d3a582bdb/main.go#L39) for more information.
 1. From a dotenv file at a path specified by the `PLUGIN_ENV_FILE` environment variable.
 2. From your `.drone.yml` Drone configuration.