[chore] Mention shouldCloseOnOverlayClick dependency

[whitecrownclown]

Mention shouldCloseOnOverlayClick dependency on onRequestClose in order to function properly.

Changes proposed:

• add mention that shouldCloseOnOverlayClick depends on having the onRequestClose prop in order to function properly when it's set to true

Acceptance Checklist:

• All commits have been squashed to one.
• The commit message follows the guidelines in CONTRIBUTING.md.
• Documentation (README.md) and examples have been updated as needed.
• If this is a code change, a spec testing the functionality has been added.
• If the commit message has [changed] or [removed], there is an upgrade path above.

[coveralls]

Coverage remained the same at 87.173% when pulling 43a339b on whitecrownclown:patch-1 into a2d5c4e on reactjs:master.

[coveralls]

Coverage remained the same at 87.173% when pulling 43a339b on whitecrownclown:patch-1 into a2d5c4e on reactjs:master.

[diasbruno]

@whitecrownclown Thank you!

[coveralls]

Coverage remained the same at 87.173% when pulling 43a339b on whitecrownclown:patch-1 into a2d5c4e on reactjs:master.

[diasbruno]

Related #462.

[diasbruno]

@whitecrownclown can you add to your commit message [chore]?

[whitecrownclown]

@diasbruno I believe you already did, i'm not really used to contributing to github yet, i appreciate any help in getting used to it.

[diasbruno]

@whitecrownclown that was the title of the issue.

On your last git commit, try to find on your tool where you can amend or edit to the commit message (or on your terminal you can git commit --amend -m "[chore] {the message}".

[diasbruno]

@whitecrownclown Thank you so much. Your commit is 92c23b5.