feat: add "install" command

### Description

What's your workflow when adding a dependency to a package?

If it's a new one, I just run `npm install foo -w libs/my-package`

If any of the other packages already use "foo", I have to hunt down the dependency and copy-paste the version into `libs/my-package/package.json`. Only then run `npm install`

This is tedious and error prone.

### Suggested Solution

Add `syncpack install foo -w libs/package`

This can automatically follow its rules for version matching, update the relevant package.json, and then call `npm install` to actually install the dependency.

### Optional comments

I cannot rely on syncpack to fix the issue after the first "latest version" install because npm often fails to properly update the lockfile.

### Code of Conduct

- [x] I agree to follow the [Code of Conduct](https://github.com/JamieMason/syncpack/blob/main/CODE_OF_CONDUCT.md)

Start by locating the CLI command entry point and the code that applies dependency version-matching rules. Inspect the relevant package.json files, including libs/my-package/package.json, and the existing npm workflow. Done means syncpack install foo -w libs/package updates the target manifest according to the rules and then runs npm install with a correct lockfile.

Written by the indexing model from the issue text.