[HTML 5] Atomic Relevant Busy

Together 'aria-live', we can use 'aria-atomic', 'aria-relevant' and 'aria-busy' to give more information to screen reader, when should announce the changes.

For example, aria-atomic:

If you change the month from 10 to 11, it will announce the whole "18 11 1983" again.

'aria-relevant':

Rreally rare that you want to change the default value 'additional text'. it means any text change or element added to the tree will announce the changes.

'aira-busy': default false:

If set to true, then it will wait the content fully loaded to announce the changes. This should be controlled by javascript. 

Once everything are loaded, the aria-busy should be set to the false.