docs: Further explanation for why .normalize() is optional

[tofumatt]

Re: #6983 (comment)

Just a brief documentation tweak.

[noisysocks]

Thanks for going into detail!

[ellatrix]

Thanks!

[Zodiac1978]

This is unsupported in IE 11 but it's a nice-to-have feature, not mandatory.
Not normalizing the content will only affect older browsers
entirely break the app.

@tofumatt I respectfully disagree.

Pasting NFD text will break the internal search in WP and can break the search on the website (like in Firefox), spellcheck, and the display (showing the character + combining character side by side and not overlaying it, Firefox is failing here for example).

And it can happen all the time that apps output NFD text and not NFC, like the W3C is recommending.

Not sure if I would call fixing this breakage "not mandatory".

[noisysocks]

@Zodiac1978: Could you please create a new issue with steps to reproduce the bug you've described? Doing this will give everyone a space to discuss the bug and possible solutions e.g. polyfilling .normalize().