[Tagging] Document personal tags in Proposed_features/ space, User: space, or Tag:/Key: space?

[Joseph Eisenberg]

All approved and de facto landforms in Map Features are under
natural=*, eg natural=ridge, natural=valley, natural=cliff,
natural=valley, natural=peak, natural=mountain_range... - it's one of
the main uses for the key natural=*, along with types of vegetation.