Ease debugging Node.js from within VSCode

[benjamn]

The other day my Chrome browser (dev channel) started crashing spontaneously on startup, which kept me from using the Chrome DevTools to debug Apollo Client tests running in Node.js.

Since I mostly use VSCode for editing these days, I decided to see if I could debug Node.js from entirely within VSCode. After all, a VSCode frontend for the V8 debugging protocol is advertised here. This would be appealing not just as a backup for Chrome, but also because it allows setting temporary breakpoints in source files (as well as inspecting local variables and the call stack) without leaving VSCode.

So far this experiment has worked out quite nicely, so this PR shares my VSCode configuration for this repository, for anyone else who wants to try this style of debugging.

Steps:

1. Add some breakpoints to a test you'd like to debug, either using debugger statements or VSCode breakpoints (click the red dot at the far left of any line)
2. Within your clone of this repository, run npm run test:debug, or npm run test:debug src/cache/inmemory to scope which tests are run
3. Switch to the debugging panel of VSCode, choose Attach to Node.js inspector from the drop-down menu towards the top, and press the green triangle to start debugging
4. Find the debugger control arrows, and press the leftmost button to continue past the very first statement in the program (likely in jest.js)
5. Wait until Node.js stops at the breakpoints you set!