Select: update docs

[silvalaura]

------ 1 ------

Description of bug: You can't select an item in MultiSelect if it has already been selected in the base select

Steps to reproduce: Open Select -> Custom Styles section -> Select an item in the Basic with custom styles select -> Try to select the same item in the Multi with custom styles select

Notes: Update examples. Ensure this is not a bigger issue when using multiple selects with similar items

------ 2 ------

Description of bug: It is unclear why we can't select an item in the Basic usage section in Bad selected item select.

Steps to reproduce: Open Select -> Basic usage section -> Try to select any item from Bad selected item select.

Notes:

We should update the example to:

1. better explain in words that items MUST be in the array
2. not have a bad selected item example at all-- it is just confusing