Fix 456/unblurred menu bar firefox

[jrgarciadev]

Closes #456

📝 Description

Due to the backdrop-filter property doesn't work on firefox, a workaround was implemented

⛳️ Current behavior (updates)

Blurred parts are displayed with transparency only on Firefox

🚀 New behavior

• docs: Navbar, Search box, Cards and other elements were modified to display a solid color instead of a blurred background on Firefox
• modal: The backdrop component was modified to display a background with transparency instead of a blurred background, only on Firefox (or browsers where the backdrop-filter property is not supported)

💣 Is this a breaking change (Yes/No): No

📝 Additional Information