Add game event handler for `LEAVE_GAME` event

[kuv2707]

Description

Following the pattern of THROW_CARD, we need to have a handler for the LEAVE_GAME event. This should reside in a file in uno-game-engine/events.

Specs

The event handler should validate the event, apply it on the respective game, and return a result indicating whether the event was successfully applied or some error occured. The leaving player's cards should be restored to the deck, and the deck should be shuffled.

Notes

• Be mindful of subtle corner cases and bugs.
• Take the existing handlers as a reference to know how handlers are supposed to work.
• Refer to the type of the event object for the event.

[issue-assigner[bot]]

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[issue-assigner[bot]]

@ritwik-69 You already have this issue assigned: issue#77 . Abandon your existing issue or contact a maintainer if you want to get this issue assigned.

[ritwik-69]

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[issue-assigner[bot]]

@ritwik-69 You already have this issue assigned: issue#93 . Abandon your existing issue or contact a maintainer if you want to get this issue assigned.

[asmit27rai]

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[issue-assigner[bot]]

@asmit27rai You already have this issue assigned: issue#84 . Abandon your existing issue or contact a maintainer if you want to get this issue assigned.

[kuv2707]

@ritwik-69 If you wish to work on a PR not assigned to you, you can leave a message letting others know you are working on it, and tag a maintainer to get it assigned to you.