docs: Expand "Start on a task" section to be more specific
    
    This improves our documentation on how to get started with design and
    development tasks in the Fedora Badges project. It includes a section on
    the things specific to Fedora Badges but also mentions the upstream
    concentricsky/badgr-server project.
    
    I added a note that these are specific to Outreachy Summer 2020, because
    it is likely this section will need to change after Outreachy. But I am
    erring on the side of being too detailed and risking it becoming
    outdated, instead of not being detailed enough to direct people to the
    right place.
    
    Also I skimped on the sysadmin docs, but I want to move our sysadmin
    docs out of the Fedora Infra SOP and into this repo so everything lives
    in one place. Once it lives here, I'll update that section too.
    
    Signed-off-by: Justin W. Flory <git@jwf.io>