feat(Text): Add a From<Cow<str>> impl for Text

[eminence]

This is useful when you have a list of Cow<str> and you want to use it in a Row.

[fdehau]

Hey 👋 . Could you add a test (maybe a doc test) to make sure this case is covered going forward ?

[eminence]

Sure! I pushed a new commit that add two examples. One is in the docs for Cell, but this was kinda boring so I also added another example in the docs for Row (which happen to mirror my own personal use case):

Row::new(vec![
    Cow::Borrowed("hello"),
    Cow::Owned("world".to_uppercase()),
]);