Add linden theme

Author: handotdev

images/themes/linden.png

@@ -33,3 +33,5 @@ There are a variety of themes to choose from.
 <ThemeCard title="Palm" description="Sophisticated fintech theme with deep customization for enterprise documentation." image="/images/themes/palm.png" href="https://palm.mintlify.app" />
 
 <ThemeCard title="Willow" description="Stripped-back essentials for distraction-free documentation." image="/images/themes/willow.png" href="https://willow.mintlify.app" />
+
+<ThemeCard title="Liden" description="Retro terminal vibes with monospace fonts for that 80s hacker aesthetic." image="/images/themes/linden.png" href="https://liden.mintlify.app" />