[Outreachy Task Submission]: Fix bulk actions accessibility

[mannyAndem]

There are currently a few issues with post bulk actions especially for users relying on the keyboard to navigate and users with low vision.

• There is no way for a user (without actually looking at the button) to know if bulk actions is enabled or not.
• When bulk actions is enabled, focus should immediately go to post checkboxes and pressing the tab key should just move over to the next post's checkbox so users relying on keyboard are more efficient.

[mannyAndem]

Fixed the issue and submitted a pr :)