fix: resolving react unique key prop warning error

[DiljohnSingh]

Pull request type

Bug fix (non-breaking change which fixes an issue)

Description

• Added index as fallback key to avoid react warnings in case of non repeated element.
• Fixed the typo in test cases
• Updated the Changelog
• Updated package.xml and package.json with new version 1.2.3

What should be covered while testing?

• Try to use the current version of HTML element widget on page as non repeated element.
• Check in console both mendix studio pro and browser to see React warning.
• Use the widget in your project after building the widget from branch, warning should not be removed.