Replace deprecated usage of CloudinaryContext #41

Bug report for Cloudinary Flutter SDK

The usage of the class CloudinaryContext has been marked as deprecated and there is a suggestion to use the CloudinaryObject instead. But, inside CldImageWidgetand CldVideoController there is usage of the CloudinaryContext to get the Cloudinary object reference.

I believe this should be replaced.

Describe the bug in a sentence or two.

Issue Type (Can be multiple)

[ ] Build - Can’t install or import the SDK
[ ] Performance - Performance issues
[ ] Behaviour - Functions aren’t working as expected (Such as generate URL)
[X] Documentation - Inconsistency between the docs and behaviour
[X] Other (Specify)

Steps to reproduce

N/A

Error screenshots or Stack Trace (if applicable)

N/A

Build/Dependency management

[ ] Cocoa-Pods
[ ] Carthage
[ ] Manual import
[ ] Other (Specify)

Is the issue reproducible only on a specific device?

[X] No
[ ] Yes (specify device model + iOS/Android version)

Versions and Libraries (fill in the version numbers)

Unrelated

Relates to #31