Add `snoc` to Data.Vect
Add `snoc` to Data.Vect

Snoc add an element at the end of the vector. The main use case
for such a function is to get the expected type signature
Vect n a -> a -> Vect (S n) a instead of
Vect n a -> a -> Vect (n + 1) a which you get by using `++ [x]`

Snoc gets is name from `cons` by reversin each letter, indicating
tacking on the element at the end rather than the begining.
`append` would also be a suitable name.

mmhelloworld/idris-jvm,mmhelloworld/idris-jvm,mmhelloworld/idris-jvm,mmhelloworld/idris-jvm,mmhelloworld/idris-jvm,mmhelloworld/idris-jvm