Add docs for canceling account
Back out premature fonts reference
Polish up cancel account
Add doc on configuring PayPal
Fix casing of GitHub
Modify Run Support to refer to new pages

I inadvertently duplicated content! We had instructions for canceling
accounts and configuring PayPal on the Run Support page. I've modified
that page to link to the new docs. I moved the "Required Access" info to
the new pages.
Fix casing of Freshdesk
Updated configure paypal instructions from discussion in #2177.

See also #2294 for a request that means this will actually work
(right now it should work, but we try to load heroku environment
from inside heroku, which fails).
Note Cheers on See Also
Tweak gfm implementation to convet ``` to <pre>
Factor out docs on script subsystem

It's too brittle to have granular script docs inline on policy pages.
Instead let's just point to the relevant script and rely on --help and
source on the script itself for granular script docs.

That said, our sript subsystem is complex enough to deserve it's own
procedure doc.
Fix typo in Run Payday
Actually put payday in the background
Merge branch 'master' into simplify-mission