Update dev script

[adityanaag3]

What does this PR do?

Updates the dev script in package.json to use LWR's built-in dev command. This removes the need to use environment variables to set server mode as 'dev'

What issues does this PR fix or reference?

TCF-036794: The line "dev": "MODE=dev node scripts/start-server.mjs" in package.json only works in mac and linux and not in windows for windows. I had to change it to "dev": "set MODE=dev&& node scripts/start-server.mjs" for it to work.

The PR fulfills these requirements:

[x] Tests for the proposed changes have been added/updated.
[x] Code linting and formatting was performed.

[github-actions]

⚠️ CodeTour Watch

Changed files with possible CodeTour impact:

• package.json

Impacted CodeTour files:

• .tours/using-third-party-javascript-libraries.tour - ⚠️ Missing from PR

Make sure to review CodeTour files and update line numbers accordingly.

[pozil]

As discussed, I updated the clean script to make it cross OX compatible.
Unlike for the E-Bikes Manufacturing demo I went for a simple rimraf module instead of the full shx cross OX shell module since we only use rm -fr here.