Introduce and explain the "falsy" term

Hello

Huge thanks for your valuable tutorial, I am re-working with JS and because JS itself evolves I am refreshing my knowledge with your tutorial

Just in case in the following page

* https://javascript.info/logical-operators

Appears many times the "falsy" term. I thought it was an error but actually it is a valid term in JS

It indicated at (and in other pages):

* https://developer.mozilla.org/en-US/docs/Glossary/Falsy

Therefore consider in add a special note indicating why is used the "falsy" term and not "false" (as is expected at first glance)

Thanks for your understanding

Open the https://javascript.info/logical-operators page and compare its use of “falsy” with the MDN Falsy glossary linked in the issue. Add a brief note explaining why JavaScript uses “falsy” rather than “false”; the page should clearly define the term for readers encountering it.

Written by the indexing model from the issue text.