Create new roles module, add D&I Advisor doc (closes #89)
    
    This commit makes the following changes:
    
    * Antora: Create new roles module for role handbooks
    * roles: Add D&I Advisor role page (closes #89)
    
    This commit creates a new Antora module called `roles`. This module will
    be a place to collect profiles of team responsibilities and how you can
    contribute to the team. For now, it will just feature the D&I Advisor
    role, but I am excited to see this expand to other things too.
    
    This commit also adds a first draft of the D&I Advisor role to the docs
    page. This page was adapted from the existing document in the Council
    docs repo:
    
    	https://docs.fedoraproject.org/en-US/council/diversity-advisor/
    
    I used this as a base and modified it. I plan to follow up with a Pull
    Request to the council-docs repo to remove that page and replace links
    with redirects to the D&I Team docs page.
    
    I did make changes though. I used the FESCo representative role page for
    many of the additions around duration and the selection process:
    
    	https://docs.fedoraproject.org/en-US/fesco/Fedora_Council_Engineering_Rep/
    
    Closes #89. Finally!
    
    Signed-off-by: Justin W. Flory (he/him) <git@jwf.io>