Clarify "outside" semantics in <annotation-position>

[palemieux]

Shouldn't "outside" mean "before" if there is only one line?

The current prose states [outside] is equivalent to before for all but the last affected line area; otherwise, equivalent to after for the last affected line area, which translates to "after" if there is only one line (which is also the last).

[cconcolato]

outside should indeed mean before when there is one line. We could rephrase by saying "if there is one line, outside is equivalent to before; otherwise ..."

[cconcolato]

As discussed in #798 (review), the clarification is also be about more than 2 lines, and for alignment with rubyReserve (#811).

[skynavga]

Merged early per WG resolution.