Add -o --output and -i or --in-file arguments.

-o or --output : write in an output file instead of stdout
-i or --in-file : Do the modification directly in the opened file.

You can start your open source contribution in this repo.

You can add a few mongoDB snippets and a two-line explanation of what it does!

For a faster merge please mention me in the comments.

Making a pull request by just correcting the typo will not be accepted!

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