Fixes #494 Add optional abort for onResizeStart

[Samuel-Lewis]

Add optional return boolean when calling onResizeStart to early exit and abort the resize sequence

Proposed solution

(From ticket #494)
Currently, when onResizeStart is called, the user provided onResizeStart (from props) is also called. In certain scenarios, however, some condition may be hit where the user wants to abort the resize.

The feature request would be to allow the user to return a boolean from their defined onResizeStart, and if it returns false, the re-resizable's onResizeStart would have an early exit and not cause any resizing.

Tradeoffs

Should not add any overheard or tradeoffs. This onResizeStart is only stopped if the user returns an explicit false. I'm sure there are many cases where the return is undefined, which should be unaffected by this change.

Testing Done

Confirmed locally in project. Added a test that initiates a resize, but immediately aborts. While the 'user' continues to resize, it checks the state isResizing state of the Resizable (should be false).

[Samuel-Lewis]

@bokuweb I'm not sure why the build failed. Could you possibly rerun it?

[bokuweb]

@Samuel-Lewis Sorry I missed it. I'll check it later.

[bokuweb]

@Samuel-Lewis LGTM

[bokuweb]

@Samuel-Lewis Please try v6.0.0 :)