CB-12129 (android): Add ability to set dialog style

[hvaughan3]

Platforms affected

Android

What does this PR do?

Created new setAndroidStyleName function to allow specifying the name of a style to apply to dialogs on Android. Also updated README to explain how to create a named style and copy it to the correct location.

What testing has been done on this change?

Tested on Android 7.1.1 emulator.

Checklist

• Reported an issue in the JIRA database
• Commit message follows the format: "CB-3232: (android) Fix bug with resolving file paths", where CB-xxxx is the JIRA ID & "android" is the platform affected.
• Added automated test coverage as appropriate for this change.

[jcesarmobile]

Thanks for the PR, but CB-12129 is closed and it's not exactly the same as what you implemented. So it's better if you create a new issue and use the new id instead of CB-12129.

Also, for new features, specially if they are platform specific, is recommended to send a mail to the cordova dev list ( dev@cordova.apache.org ) so it can be discussed.