fix(css): resolve relative imports in sass properly on Windows

[sapphi-red]

Description

fileURLToPath('file:///C:/foo.js', { windows: false }) returns /C:/foo.js. Even with this output, it still worked because the internal resolve plugin supports that format (/C:/foo.js) as well.

vite/packages/vite/src/node/plugins/resolve.ts

Lines 262 to 274 in 16a73c0

	// URL
	// /foo -> /fs-root/foo
	if (
	asSrc &&
	id[0] === '/' &&
	(rootInRoot || !id.startsWith(withTrailingSlash(root)))
	) {
	const fsPath = path.resolve(root, id.slice(1))
	if ((res = tryFsResolve(fsPath, options))) {
	debug?.(`[url] ${colors.cyan(id)} -> ${colors.dim(res)}`)
	return ensureVersionQuery(res, id, options, depsOptimizer)
	}
	}

But the expected result here for this input is C:/foo.js, and this PR fixes the condition to use windows option.