This package provides the ShortText type which is suitable for keeping many
short strings in memory. This is similiar to how ShortByteString relates
to ByteString.

The main difference between Text and ShortText is that ShortText doesn't support
zero-copy slicing (thereby saving 2 words), and, compared to text-1.*, that it
uses UTF-8 instead of UTF-16 internally. Consequently, the memory footprint of a
(boxed) ShortText value is 4 words (2 words when unboxed) plus the length of the
UTF-8 encoded payload.
