Feature request: getSupportedPreviewSizes

[capc0]

In order to know which dimensions are supported for setPreviewSize, a function for getting the supported sizes would be needed. I tried getSupportedPictureSizes, but not all of them are supported as the preview size, and there is no way to tell if a valid picture size is also a valid preview size.

It seems like it once already existed, but was removed from the codebase? #199

Android https://developer.android.com/reference/android/hardware/Camera.Parameters#getSupportedPreviewSizes()

It is also already used internally, but not exposed https://github.com/cordova-plugin-camera-preview/cordova-plugin-camera-preview/blob/master/src/android/Preview.java#L55