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

Abra a página https://javascript.info/logical-operators e compare o uso de “falsy” nela com o MDN Falsy glossary vinculado na issue. Adicione uma breve observação explicando por que o JavaScript usa “falsy” em vez de “false”; a página deve definir claramente o termo para leitores que se deparam com ele pela primeira vez.

Escrita pelo modelo de indexação a partir do texto da issue.