Added warning if no event system for consent form interaction

[manwithsteelnerves]

Title

Added a warning to inform the user to add an Event System when consent form is presented.

Reason

Without an Event System in the scene and presenting the consent for in unity editor or non-supported platforms makes the button in consent form non-interactable.

Solution

Fixed this by adding a warning when consent form is presented to inform the user to take necessary action.

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