[docs] accordion: update to include left alignment

[aagonzales]

After discussion in our design crit on 6/6/21 with Mike Gower we've decided to update our accordion usage to allow for either end or start side alignment of the chevron. End alignment is still preferred however some use-case merit start alignment.

Start alignment is beneficial when the accordion width is very wide and the chevron indicator become disassociated with the content. See accessibility website for example.

Remove this as a don't. Change to a with caution?