Deep linking issue

Hello!

when using the plugin to open a web page that uses deep linking - open another app -, the plugin does not open the app.

## System info

Issue occurs on: both
Plugin version: 0.3.22+1
Flutter doctor output:

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## Steps to Reproduce

Open a web page that uses deep linking to open another app.

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[√] Flutter (Channel stable, v1.17.3, on Microsoft Windows [Version 10.0.18362.900], locale en-US)
• Flutter version 1.17.3 at C:\flutter
• Framework revision b041144f83 (4 weeks ago), 2020-06-04 09:26:11 -0700
• Engine revision ee76268252
• Dart version 2.8.4

[!] Android toolchain - develop for Android devices (Android SDK version 29.0.2)
• Android SDK at C:\Users\Hasan\AppData\Local\Android\sdk
• Platform android-29, build-tools 29.0.2
• Java binary at: C:\Program Files\Android\Android Studio\jre\bin\java
• Java version OpenJDK Runtime Environment (build 1.8.0_242-release-1644-b01)
! Some Android licenses not accepted. To resolve this, run: flutter doctor --android-licenses

[√] Android Studio (version 4.0)
• Android Studio at C:\Program Files\Android\Android Studio
• Flutter plugin version 46.0.2
• Dart plugin version 193.7361
• Java version OpenJDK Runtime Environment (build 1.8.0_242-release-1644-b01)

[√] VS Code (version 1.46.1)
• VS Code at C:\Users\Hasan\AppData\Local\Programs\Microsoft VS Code
• Flutter extension version 3.11.0

[√] Connected device (1 available)
• Android SDK built for x86 • emulator-5554 • android-x86 • Android 9 (API 28) (emulator)

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该 issue 未指定源文件或测试。首先在报告所涉及的平台上使用 flutter_webview_plugin 0.3.22+1 复现深层链接流程，然后检查插件对原生 WebView 的处理。完成标准是：调用另一个应用的网页能在两个平台上正确打开该应用。

由索引模型根据 Issue 内容生成。