This commit clarifies the purpose of this README for two things: event
reimbursement requests and swag shipment requests. The templates added
in commit a806bf3a

 are explicitly linked
from the README along with some pre-generated information for the issue
title. The motivation for these changes is to reinforce the correct
process for these two types of activities while also making it easier
for the requester by not requesting duplicate information. It also gets
the requester to share strategic information about the event in the open
ticket in the Mindshare Committee repository.

Signed-off-by: Justin W. Flory (he/him) <jwf@redhat.com>