Fix: Configuration and Setup instructions

[seangwright]

Motivation

• Add instructions to the Contributing Setup doc for Admin UI customizations & webpack dev server
  • Update VS Code tasks with correct dependent tasks
• Update test and C# analyzer NuGet packages to latest versions
• Fix C# analyzer warnings
• Update npm packages to latest version and set correct Node.js version requirement
• Update CI pipeline to use required Node.js version for builds

Checklist

• Code follows coding conventions held in this repo
• Automated tests have been added
• Tests are passing
• Docs have been updated (if applicable)
• Temporary settings (e.g. variables used during development and testing) have been reverted to defaults

How to test

If manual testing is required, what are the steps?