Provide an API to load all types available in `node_modules/`

[wojpawlik]

Is your feature request related to a problem? Please describe.

I hoped https://npm.im/deno2node could sourceFile.fixMissingImports() to import fetch and AbortController ponyfills, but:

the JS language service doesn't aggressively include types for packages it can't tell you're using yet, because doing so would be a fairly substantial perf hit for not a lot of gain. (microsoft/TypeScript#29039 (comment))

Describe the solution you'd like

Provide a (Project) method for loading all types from all packages at the top-level of node_modules/.

[dsherret]

I'm not sure how to do this with the TS compiler and it would take some investigative work. A hacky way around this might be to temporarily add import "abort-controller";-like dummy imports then do fixMissingImports() then remove them (I'm not sure it would work though).

[wojpawlik]

I no longer need this: wojpawlik/deno2node#4