Optimized visual experience

1. Optimized for Chinese Characters (Noto Serif).
   • smaller font-size.
   • add bold font-weight of Noto Serif.
2. Add support for tag </ruby> to make up Furigana in Japanese..
3. Changed copyright info in footer.
4. Change visual experience of lightlight code blocks.
   • background color
   • block width

Add Font support for CJK

Add Google Noto Serif Font Family, regular.

• noto-serif-sc-v21-chinese-simplified-regular
• noto-serif-tc-v22-chinese-traditional-regular
• noto-serif-jp-v20-japanese-regular