Is it possible to set background color of web view?

# Feature Request

## Motivation Behind Feature
When use in-app-browser to view am image, the background color will show in white.

## Feature Description
set background color of web view.

The issue names no file, test, or platform entry point. Start by locating the plugin's Android and iOS web-view implementations and check how view appearance is configured. Done means users can set the in-app browser web view's background color, with coverage for the supported platforms.

Written by the indexing model from the issue text.