Provide an editor-level warning when including output files

Something that we noticed with internal codebases, as well as even with RxJS is that tsconfig.jsons are incorrectly configured for editor scenarios and include folders like dist and lib. This means you end up with slower performance, and noisy auto-imports.

We already provide some sort of error here when compiling, but we don't provide the same error in editor scenarios.

Open questions:

• How is this information presented to the user? How is the editor given notice that it should alert a user about this?
• What exactly does it mean to include an output file? In the case of RxJS, there are no "output files" getting included in the compilation based on how we determine a file is an an output of input files. Specifically, the root-level tsconfig.json doesn't specify an outDir, so it doesn't know that it should avoid including dist. Maybe we can use some directory-naming heuristics when we find one folder named src and another named dist or lib?

Start with the existing compiler error for projects that include output files and compare how the same tsconfig.json is handled in editor scenarios. Clarify how the editor should be notified and what counts as an output file, then define the warning behavior and detection rules as done criteria.