Basic template support for Jest + VSCode, type-check tests

[sramam]

Current Behavior

I am using tsdx to setup a headless monorepo, meaning I use the basic template. Very useful. So thank you.

However, to get VSCode + jest to work correctly on the test files, I keep having to make this adjustment to tsconfig.json

Expected behavior

My needs don't seem special and I'd suspect these should be the defaults in the template.

[agilgur5]

This is effectively a duplicate of #871 and I've documented that one extensively, so I'll leave most of the details to it.

Some issues with your set-up that you may have later discovered:

• include: test can't be added there as it will make it so your tests are also compiled. Other than that being unnecessary, it could also affect directory structure etc. In https://github.com/jaredpalmer/tsdx/issues/871#issuecomment-695822562, I recommend using a tsconfig.build.json to get around this -- one tsconfig for type-checking all your files, one for building specific files.
• types: you may be misunderstanding how tsconfig's types field works. this will make it ignore all @types libraries except for @types/jest, which I don't think you mean to do. I recommend using @jest/globals (or jest-without-globals for older versions of Jest) to avoid globals entirely, but if you are using globals, TSDX already comes installed with @types/jest, which TypeScript will automatically detect and use in your node_modules so long as your typeRoots and types haven't been configured otherwise
• rootDir: see the comment in the tsconfig.json as well as https://github.com/jaredpalmer/tsdx/issues/871#issuecomment-695822562 's various links