[RailsDevs] Add a tooltip to the headers on the admin conversations dashboard

The admin conversations dashboard lets admins keep up with ongoing conversations happening between businesses and developers.
It's not very obvious what two columns, REPLIED? and EMAIL?, mean.
A PR addressing this issue should:
•  Add a title HTML attribute to the two headers explaining what they do.

The HTML title attribute appears as a tooltip when hovering the element. Use the following titles:
• REPLIED? - The developer has replied to this conversation.
• EMAIL? - The developer mentioned an email address in a reply.

This will most likely require changing the Admin::Tables::HeaderComponent View Component to accept a new attribute to be rendered.