Intersperses the given character between the 
YiStrings. This is
useful when you have a bunch of strings you just want to separate
something with, comma or a dash. Note that it only inserts the
character between the elements.
What's more, the result is a single 
YiString. You can easily
achieve a version that blindly inserts elements to the back by mapping
over the list instead of using this function.
You can think of it as a specialised version of 
intercalate.
Note that what this does 
not do is intersperse characters into
the underlying text, you should convert and use 
intersperse for
that instead.