Updated article: Normalization in HTML and CSS

The article Normalization in HTML and CSS 
<https://www.w3.org/International/questions/qa-html-css-normalization.en> 
was largely rewritten. It now describes the various normalization forms, 
and clarifies that W3C doesn’t require all content to be strictly 
NFC-normalized. It also warns about the dangers of blindly normalizing 
content to a particular normalization form (unless performing a 
match/sort procedure).

Translators are requested to update the translations in German, Spanish, 
French, Polish, Brazilian Portuguese, Russian, and Ukrainian.