Add code contribution docs

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The docs will be expanded to cover contributing to the ResearchEquals codebase. We can use this thread to document any relevant tidbits to synthesize in the contributing docs.

Some initial redwood commands that are relevant, for the development of dev.researchequals.com:

# Create a new component
yarn rw g component <name>

# Migrate the database
yarn rw prisma migrate dev
# Open the database studio env
yarn rw prisma studio

# TODO - sort these commands
yarn rw g scaffold <model>
yarn rw prisma format

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yarn rw storybook