propose example element for documentation and other uses

[Nick-Levinson]

For communicating about HTML, teaching it, or other purposes, with an example that should not cause an actual effect in a user agent, even a user agent programmed for private use, a tag name should be specified for the purpose and HTML should specify it. I propose "example" for an element using either only one tag or two tags.

Case, spacing, and the slash would have the same rules as for other elements.

If there are two tags enclosing content, the content would be processed by a user agent as if those tags were absent.

An analogy is with domain names, such as example.com and *.test.

[chaals]

Duplicated by #1042

[chaals]

(Well, almost. That requests an attribute instead of element, but I think the two can be readily combined and that the problem is about the same).