Add word Supercalifragilisticexpialidocious

[gagandixit]

Add all the definitions of [Word] in a file named [Word].json in folder [First-Letter]

Refer CONTRIBUTING.md for more details on how to contribute.

Comment the words you'll be adding if you're are working on this issue to avoid conflicts.
Add reference to this issue i.e Issue # in your pull request description.

[welcome]

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[anuragshukla07]

I want to contribute on this issue. Please assign me this.

[gagandixit]

I want to contribute in this issue. /assign