feat: add stackly popup

[berteotti]

Fixes: #swa-62

Description

This PR adds stackly popup in yellow and green type. Advise to test it on preview link (or build it locally) then to test it locally, will fail to show the modal due to how react works locally.

To make it work don't forget to set env variables:

REACT_APP_STACKLY_POPUP_COLOR=yellow REACT_APP_SHOW_STACKLY_POPUP=true

How to test the changes

I advise to test it in the preview. Once you close the only way to see it again is through cleaning local storage.

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[wixzi]

The code works as expected. Good Job @berteotti . Have some minor suggestions on variable names. If you feel my suggestions are better then only change them.

[0xVenky]

Lookie good! Letsssgooo

[Diogomartf]

Looking good!