fix: Modified setup instructions for new developers

[AndrewWestberg]

This PR Updates the setup instructions for NIX and how to get around a common sandbox error when launching Daedalus in dev mode.

Testing Checklist

N/A. This is a doc-only change.

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Review Checklist

Basics

• PR assigned to the PR author(s)
• input-output-hk/daedalus-dev and input-output-hk/daedalus-qa assigned as PR reviewers
• If there are UI changes, Alexander Rukin assigned as an additional reviewer
• PR has appropriate labels (release-vNext, feature/bug/chore, WIP)
• PR link is added to a Jira ticket, ticket moved to In Review
• PR is updated to the most recent version of the target branch (and there are no conflicts)
• PR has a good description that summarizes all changes
• PR contains screenshots (in case of UI changes)
• CHANGELOG entry has been added to the top of the appropriate section (Features, Fixes, Chores) and is linked to the correct PR on GitHub
• There are no missing translations (running yarn manage:translations produces no changes)
• Text changes are proofread and approved (Jane Wild / Amy Reeve)
• Japanese text changes are proofread and approved (Junko Oda)
• Storybook works and no stories are broken (yarn storybook)
• In case of dependency changes yarn.lock file is updated

Code Quality

• Important parts of the code are properly commented and documented
• Code is properly typed with typescript types
• React components are split-up enough to avoid unnecessary re-renderings
• Any code that only works in main process is neatly separated from components

Testing

• New feature/change is covered by acceptance tests
• New feature/change is manually tested and approved by QA team
• All existing acceptance tests are still up-to-date
• New feature/change is covered by Daedalus Testing scenario
• All existing Daedalus Testing scenarios are still up-to-date

After Review

• Update Slack QA thread by marking it with a green checkmark

[michalrus]

That’s great! Thank you very much 🙌