Fix missing unique key prop in Contributors.js

[RTEYL]

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in components/layouts/Contributors.js contributors are mapped but the box component does not have a unique key prop

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provide the box component with a key prop to avoid errors and error messages

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{contributors.map((contributor) => (

// add prop key={some_unique_value} to Box component or key={contributor._id)}
        <Box component='span' m={0} id={contributor._id}>
          <Typography component='p'>{contributor.name}</Typography>
          <Link href={contributor.link}>see more...</Link>
        </Box>
      ))}