Add method isEnabled in UIElement

[dcrespim]

PR Checklist

• [ ] The PR title follows our guidelines: https://github.com/NativeScript/NativeScript/blob/master/CONTRIBUTING.md#commit-messages.
• [ ] There is an issue for the bug/feature this PR is for. To avoid wasting your time, it's best to open a suggestion issue first and wait for approval before working on it.
• [ ] All existing tests are passing
• [ ] Tests for the changes are included

What is the current behavior?

Add access to enable property on UIElement

What is the new behavior?

Publish isEnabled property to access driverIO Element enable.

Fixes/Implements/Closes #[Issue Number].

N/A

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[cla-bot[bot]]

Thank you for your pull request and welcome to our community. We could not parse the GitHub identity of the following contributors: David Crespi. This is most likely caused by a git client misconfiguration; please make sure to:

1. check if your git client is configured with an email to sign commits git config --list | grep email
2. If not, set it up using git config --global user.email email@example.com
3. Make sure that the git commit email is configured in your GitHub account settings, see https://github.com/settings/emails