Add emoji flag support

[DustinWin]

Checklist

• I have read and accepted the contributing guidelines.

Is your feature request related to a problem? Please describe

The content inside the <code>, <kbd> and <pre> tags cannot be displayed correctly when they contain emoji flags.

Describe the solution you'd like

Add the Noto Color Emoji font, address: https://fonts.google.com/noto/specimen/Noto+Color+Emoji, then define a new css style and add the Noto+Color+Emoji font to the font-family of the <code>, <kbd>, and <pre> tags.

Describe alternatives you've considered

No response

Additional context

No response