docs: improve forms cards

docs/content/3.forms/3.select.md

@@ -38,6 +38,8 @@ props:
 
 ### Placeholder
 
+Use the `placeholder` prop to set a placeholder text.
+
 ::component-card
 ---
 baseProps:
@@ -83,14 +85,13 @@ baseProps:
     - 'United States'
     - 'Canada'
     - 'Mexico'
+  placeholder: 'Search...'
 props:
   icon: 'i-heroicons-magnifying-glass-20-solid'
   appearance: 'white'
   size: 'sm'
-  placeholder: 'Search...'
 excludedProps:
   - icon
-  - placeholder
 ---
 ::
 
@@ -106,12 +107,10 @@ baseProps:
     - 'United States'
     - 'Canada'
     - 'Mexico'
-props:
   placeholder: 'Search...'
+props:
   appearance: 'white'
   disabled: true
-excludedProps:
-  - placeholder
 ---
 ::