This moves YAML formatting behind an unstable flag for Deno 1.46. This
will make it opt-in to start and then we can remove the flag to make it
on by default in version of Deno after that.
This can be specified by doing `deno fmt --unstable-yaml` or by
specifying the following in a deno.json file:
```json
{
"unstable": ["fmt-yaml"]
}
```
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
