dub silently ignores misspelt keys

[Laeeth]

change 'dependency' in a dub.sdl file to 'dependecy' - dub doesn't warn about the spurious entry but just proceeds as if the line were blank. it should at least issue a warning (and maybe could use Levenshein distance to suggest what you might have meant)

[Geod24]

This is handled in dub.json, but not in dub.sdl.