This PR implements the changes we plan to make to `deno install` in deno
2.0.
- `deno install` without arguments caches dependencies from
`package.json` / `deno.json` and sets up the `node_modules` folder
- `deno install <pkg>` adds the package to the config file (either
`package.json` or `deno.json`), i.e. it aliases `deno add`
- `deno add` can also add deps to `package.json` (this is gated behind
`DENO_FUTURE` due to uncertainty around handling projects with both
`deno.json` and `package.json`)
- `deno install -g <bin>` installs a package as a globally available
binary (the same as `deno install <bin>` in 1.0)
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Co-authored-by: Nathan Whitaker <nathan@deno.com>
