Support other workspace: specifiers

[bartlomieju]

Currently Deno supports workspace:* specifiers in package.json, but tools like pnpm also support
workspace:^, workspace:~ and others.

See https://pnpm.io/workspaces#publishing-workspace-packages

Necessary changes would need to be applied around this code:
https://github.com/search?q=org%3Adenoland+PackageJsonDepValue%3A%3AWorkspace&type=code

[bartlomieju]

I did some digging into this and here's what I found:

1. Handling of workspace: specifiers in package.json is done here: https://github.com/denoland/deno_package_json/blob/bf59efc107b0d7191018e0d06ef1341f86fe6c1b/src/lib.rs#L346
2. The workspace: prefix is stripped and the remainder is passed to VersionReq::parse_from_npm from deno_semver: https://github.com/denoland/deno_semver/blob/6fba7fd973fc9cc77a54c1412d0e2a0fb357730f/src/npm.rs#L92
3. * or x.y.z are valid ranges in this context, but ~ and ^ are not
4. It appears that simply stripping workspace: is not good enough here and we should have a dedicated functionality in deno_semver to handle workspace: version constraints that will accept ~ and ^, otherwise we'd have to alter the current parsing which would break other stuff, because "mypackage": "^" is not a valid range, but "mypackage": "workspace:^" is.

@dsherret do you agree here?

[dsherret]

It looks good, but I think we probably dont' need any changes in deno_semver. Probably it could just be handled in deno_package_json (I'm not sure though)