fix(create-vite): update templates to use better font

[mayank99]

Description

Hardcoding a pixel value for font-size on the root element is bad for accessibility because it overrides user preferences (specified in browser/OS settings). 16px is already the default in all modern browsers, so I've removed it. For line-height, a unitless value is recommended, so I've used 1.5 (because 1.5 x 16 = 24). Any changes so far should be minimal.

I know this is just a template that gets cleared by most devs. But even templates should encourage best practices; it's especially handy for new devs.

Unrelated: While I was there, I also added system-ui to the font stack. This is an OS-adaptive font that should look nice on every platform. I can undo this change if it's undesirable.

Additional context

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What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

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[bluwy]

Thanks @mayank99! If you'd like, there's tons more to update at https://github.com/bluwy/create-vite-extra too. Otherwise I can also update them when I find the time.