Implement borzoi-lock.json

[Aarush-Goyal]

As discussed in the issue

Does it support cloning a specific branch of a repo or at a specific commit ? #27

The state of all repositories at the particular time would be stored using a borzoi-lock.json file.

The file will be made using the command borzoi freeze.

The lock file will be used to clone when borzoi clone and only the borzoi-lock.json file is found in the current directory otherwise if both borzoi.json and borzoi-lock.json are found then the user can run borzoi clone --frozen command to use the lock file to clone repos.

[Aarush-Goyal]

@automation-co/open-source-team Would be providing updates as the progress is made.