Example project not working on web

The example project is not working with flutter web, https://pub.dev/packages/flutter_webview_plugin#-readme-tab- this page states that this plugin supports flutter web. But loading an url does not seem to work.

Does this plugin really support web??

## System info

Issue occurs on: Web
Plugin version: 0.3.11
Flutter doctor output:

```
Doctor summary (to see all details, run flutter doctor -v):
[✓] Flutter (Channel beta, 1.18.0-11.1.pre, on Linux, locale en_US.UTF-8)
[✓] Android toolchain - develop for Android devices (Android SDK version 29.0.3)
[✗] Chrome - develop for the web (Cannot find Chrome executable at google-chrome)
! Cannot find Chrome. Try setting CHROME_EXECUTABLE to a Chrome executable.
[✓] Android Studio (version 4.0)
[✓] Android Studio (version 3.6)
[✓] Connected device (1 available)

! Doctor found issues in 1 category.

```

## Steps to Reproduce

1. Open example project from github
2. Run project for flutter-web
3. Click on any button
4. Nothing happens

Only clicking on "open widget web view" seems to do something. But only the `initialChild` is displayed.

## Logs

As far as the console logging works in the browser, this is the output:

```
dart.developer.postEvent Flutter.Navigation {"route":{"description":"MaterialPageRoute(/widget)","settings":{"name":"/widget"}}}
```

```
[✓] Flutter (Channel beta, 1.18.0-11.1.pre, on Linux, locale en_US.UTF-8)
• Flutter version 1.18.0-11.1.pre at /home/y/Documents/flutter/flutter
• Framework revision 2738a1148b (3 weeks ago), 2020-05-13 15:24:36 -0700
• Engine revision ef9215ceb2
• Dart version 2.9.0 (build 2.9.0-8.2.beta)

[✓] Android toolchain - develop for Android devices (Android SDK version 29.0.3)
• Android SDK at /home/y/Android/Sdk
• Platform android-29, build-tools 29.0.3
• Java binary at: /snap/android-studio/90/android-studio/jre/bin/java
• Java version OpenJDK Runtime Environment (build 1.8.0_242-release-1644-b3-6222593)
• All Android licenses accepted.

[✗] Chrome - develop for the web (Cannot find Chrome executable at google-chrome)
! Cannot find Chrome. Try setting CHROME_EXECUTABLE to a Chrome executable.

[✓] Android Studio (version 4.0)
• Android Studio at /snap/android-studio/90/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-b3-6222593)

[✓] Android Studio (version 3.6)
• Android Studio at /snap/android-studio/88/android-studio
• Flutter plugin version 45.1.1
• Dart plugin version 192.8052
• Java version OpenJDK Runtime Environment (build 1.8.0_212-release-1586-b4-5784211)

[✓] Connected device (1 available)
• Web Server • web-server • web-javascript • Flutter Tools

! Doctor found issues in 1 category.

```

example project と README の Flutter web-support claim から始め、次に Flutter web 向けにプロジェクトを実行して、記載されているボタンの手順に従う。URL の読み込みと web view が説明どおりに動作するか確認する。完了条件は、web support の状態と観測された動作が解決済みまたは明確に文書化されていること。

索引モデルが issue の本文から書いたものです。