[CONTRACT] Create a "Greeting" Function

[Sadeequ]

Desc: A function hello(user: Symbol) -> Vec<Symbol> that returns "Hello", user.

Goal: Tests basic Vec manipulation and symbol handling.

[Abdul-dev-creator]

@Abdul-dev-creator has applied to work on this issue as part of the Stellar Wave Program's 3rd wave.

Gm i will like to be assigned to this task

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