fix: typos in apps/ui-playground (#21223)

Found via codespell

Co-authored-by: Alex van Andel <me@alexvanandel.com>

apps/ui-playground/content/design/components/button.mdx

@@ -58,7 +58,7 @@ Buttons can be grouped together using the ButtonGroup component. The ButtonGroup
 
 ### Button Group Sizes
 
-#### Seperated
+#### Separated
 
 <ButtonGroupSizes/>
 

apps/ui-playground/content/design/components/textarea.sizes.tsx

@@ -9,7 +9,7 @@ export const SizesExample: React.FC = () => (
     <div className="space-y-4 md:w-80">
       <div className="space-y-2">
         <h3 className="text-emphasis text-sm">Default Height</h3>
-        <TextAreaField name="deafult" placeholder="Default height textarea..." />
+        <TextAreaField name="default" placeholder="Default height textarea..." />
       </div>
 
       <div className="space-y-2">