Introduces a new lockfile format that will be used to support locking
"npm" dependencies.
Currently the format looks as follows:
```
// This file is automatically generated by Deno, do not edit its contents
// manually. This file should be commited to your repository.
{
"version": "2",
"remote": {
"https://deno.land/std@0.160.0/http/server.ts": "asdwetsw44523asdfgfas..",
"https://deno.land/std@0.160.0/http/file_server.ts": "asdwetsw44523asdfgfas.."
}
}
```
A follow up PR will add "npm" key that will be used to store information
related
to "npm" dependencies and their resolution.
The new format is used when `--lock-write` is present, if user tries to
load
a lock file using the old format it will still work.
