Release 3.21.0

18 new icons:

• filled/brand-angular
• filled/brand-instagram
• filled/brand-kick
• filled/brand-linkedin
• filled/brand-open-source
• filled/brand-opera
• filled/brand-pinterest
• filled/brand-sketch
• filled/brand-snapchat
• filled/brand-steam
• filled/brand-stripe
• filled/brand-tabler
• filled/brand-tinder
• filled/brand-tumblr
• filled/brand-vercel
• filled/brand-vimeo
• filled/brand-whatsapp
• filled/brand-windows

Fixed icons: outline/brand-instagram, outline/brand-linkedin, outline/brand-tabler