Defaults values for files, maxSize and compression algorithm in cli

[anikethsaha]

Do you want to request a feature or report a bug?
feature, more like better if present.

What is the current behavior?
Currently, it does not have any default value except for the compression algorithm.

If the current behavior is a bug, please provide the steps to reproduce.
run the below command without having any config for bundlesize in package.json
$ npx bundlesize
This will be the error

 ERROR  Config not found.

    You can read about the configuration options here:
    https://github.com/siddharthkp/bundlesize#configuration

If this is a feature request, what is motivation or use case for changing the behavior?
maximum time this package can be used to do a quick clip test for the size of the project and if there can be a way to avoid these errors with the default error . Notifying the user about the default values and using it may be a good experience

Please mention other relevant information.

• node version : v10.15.3
• npm version: 6.9.0
• Operating system: Windows 10
• bundlesize version : 0.17.1
• CI you are using: None

[anikethsaha]

PTAL at the implementation