Update Wasm CI badge in README.md

Now WebAssembly target is being tested on ci.swift.org, so update the
badge in README.md to point to the correct job.

Author: kateinoigakukun

README.md

@@ -19,11 +19,16 @@
 | **Amazon Linux 2** | AArch64 |[![Build Status](https://ci.swift.org/job/oss-swift-package-amazon-linux-2-aarch64/lastCompletedBuild/badge/icon)](https://ci.swift.org/job/oss-swift-package-amazon-linux-2-aarch64)|
 | **Universal Base Image 9** | x86_64 |[![Build Status](https://ci.swift.org/job/oss-swift-package-ubi-9/lastCompletedBuild/badge/icon)](https://ci.swift.org/job/oss-swift-package-ubi-9)|
 
+**Cross-Compilation Targets**
+
+| **Target** | **Build** |
+|:---:|:---:|
+| **wasm32-unknown-wasi** |[![Build Status](https://ci.swift.org/job/oss-swift-pr-test-crosscompile-wasm-ubuntu-20_04/lastCompletedBuild/badge/icon)](https://ci.swift.org/job/oss-swift-pr-test-crosscompile-wasm-ubuntu-20_04)|
+
 **Swift Community-Hosted CI Platforms**
 
 | **OS** | **Architecture** | **Build** |
 |---|:---:|:---:|
-|**[Ubuntu 20.04](https://github.com/apple/swift-community-hosted-continuous-integration/blob/main/nodes/wasm32_ubuntu_20.04.json)** | wasm32 |[![Build Status](https://ci-external.swift.org/job/oss-swift-RA-linux-ubuntu-20.04-webassembly/lastCompletedBuild/badge/icon)](https://ci-external.swift.org/job/oss-swift-RA-linux-ubuntu-20.04-webassembly)|
 |**[Android](https://github.com/apple/swift-community-hosted-continuous-integration/blob/main/nodes/x86_64_ubuntu_16_04_LTS_android.json)** | ARMv7 |[![Build Status](https://ci-external.swift.org/job/oss-swift-RA-linux-ubuntu-16.04-android/lastCompletedBuild/badge/icon)](https://ci-external.swift.org/job/oss-swift-RA-linux-ubuntu-16.04-android)|
 |**[Android](https://github.com/apple/swift-community-hosted-continuous-integration/blob/main/nodes/x86_64_ubuntu_16_04_LTS_android.json)** | AArch64 |[![Build Status](https://ci-external.swift.org/job/oss-swift-RA-linux-ubuntu-16.04-android-arm64/lastCompletedBuild/badge/icon)](https://ci-external.swift.org/job/oss-swift-RA-linux-ubuntu-16.04-android-arm64)|
 |**[Windows 2019 (VS 2019)](https://github.com/apple/swift-community-hosted-continuous-integration/blob/main/nodes/x86_64_windows_2019_VS2019.json)** | x86_64 | [![Build Status](https://ci-external.swift.org/job/oss-swift-windows-x86_64-vs2019/lastCompletedBuild/badge/icon)](https://ci-external.swift.org/job/oss-swift-windows-x86_64-vs2019)|