Added a FAQ [skip CI]
Added a FAQ [skip CI]


Former-commit-id: acdea56677a2bac4d562d5bbea32a1cc0b237917 [formerly 7ed540ed942a138af2e050b8638c0f277010d4c3]
Former-commit-id: 4d700975533834a7f3db1d83d344c676a878eaec
gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine