doc: add Windows instructions
doc: add Windows instructions

Former-commit-id: 1716376ad2049abb14fc6552c2cbc24bb18b7348 [formerly 9874f1de0d5a4ac6b7587f5e035d03b3667b57fd]
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gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine