Provide bash completion support file

Summary:
This fixes the following issue:

bash: /opt/arcanist/support/shell/hooks/../rules/bash-rules.sh: No such file or directory

Test Plan: arc shell on Dwellers

Reviewers: dereckson

Reviewed By: dereckson

Subscribers: Nasqueron Docker deployment squad

Tags: Docker images

Differential Revision: https://devcentral.nasqueron.org/D2348