Fix Prettier and ESLint warnings

[GAsplund]

Just some general cleanup of the project.

Key features:

• New .prettierignore file to ignore certain files and directories
• Format all files with Prettier
• Fix majority of ESLint warnings:
  • Remove unused colorette package
  • Allow underscore escaped, unused arguments
  • Marked relevant unused args
  • Wrap img element in picture element (recommended by Next)

Known issues:

• Unused warnings in NotifyService are valid, but should be ignored until used elsewhere
• React complains about a function in useEffect - from my limited googling this is hard to solve without dumb solutions
• I used Prisma's recommended singleton file, but it seems like the global variable is unused. Unsure if to remove or not