A keyword may not begin with '-'.  Otherwise, "-----BEGIN" would be
a keyword, and the grammar would be ambiguous.

A beginline or endline may have multiple words in its tag.

Signed-off-by: David Goulet <dgoulet@torproject.org>

Our docs accurately describe how to remove MAPADDRESS entries, but doesn't
demonstrate it. Exemplifying how to query our mappings and remove them.

  tpo/core/tor#40104

(tjr is okay with this)

It's under discussion on tor-dev.

We've talked about these, and in some cases begun to implement them.

They are implemented, and only need (possible) spec updates

Closes #30123