Don't need to modify the launch.json, the default "Python: Current File (Integrated Terminal)" works perfectly. For the Python3 project, remember to place the runner.py file at the same level as the scrapy.cfg file (which is the project root).
The runner.py code as @naqushab does above. Note the processs.crawl(className), where the className is the spiders class that you want to set the breakpoint at.