Adds much better support for the unstable Deno workspaces as well as
support for npm workspaces. npm workspaces is still lacking in that we
only install packages into the root node_modules folder. We'll make it
smarter over time in order for it to figure out when to add node_modules
folders within packages.
This includes a breaking change in config file resolution where we stop
searching for config files on the first found package.json unless it's
in a workspace. For the previous behaviour, the root deno.json needs to
be updated to be a workspace by adding `"workspace":
["./path-to-pkg-json-folder-goes-here"]`. See details in
https://github.com/denoland/deno_config/pull/66
Closes #24340
Closes #24159
Closes #24161
Closes #22020
Closes #18546
Closes #16106
Closes #24160
This allows people to use imports like:
```ts
import "./app.css";
```
...with `deno check` in systems where there's a bundle step (ex. Vite).
This will still error when using it with `deno run` or if the referenced
file does not exist.
See test cases for behaviour.
