fontStyle and background are missed when working with monaco editor

[lejunyang]

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Describe the bug

we can see "export default" is italic style in material-theme-darker theme, while in reproduction, there is no italic style

I think fontStyle and background are missed from below

shiki/packages/monaco/src/index.ts

Lines 34 to 39 in 76cbc7e

	if (settings.foreground && s) {
	rules.push({
	token: s,
	foreground: normalizeColor(settings.foreground),
	})
	}

Reproduction

https://codepen.io/lejunyang/pen/xbKKwQO

Contributes

• I am willing to submit a PR to fix this issue
• I am willing to submit a PR with failing tests