Enhancement: Show special targetnames in the entity i/o menu dropdown

[lenship2]

What would this enhancement be for?

Hammer

Describe your enhancement suggestion in more detail

In Source 2's entity list dropdown in the i/o tab, special targetnames like !player and !self are shown as selectable options at the top of the list. This would be nice to have in Strata's hammer, and would also allow newer mappers to discover their existence more easily.

[TeamSpen210]

Definitely, was trying that a bit earlier. Ideally we'd also figure out some cleverness, so !self could show the inputs on the current entity, !player would get autocomplete for player inputs, etc.