Merge pull request #59 from jpudysz/feature/docs

docs: mention as const

docs/src/content/docs/example/variants.mdx

@@ -97,6 +97,8 @@ const stylesheet = createStyleSheet(theme => ({
     }
 }))
 ```
+Remember, that if you want to spread styles like so you need to export your theme "as const" for TypeScript.
+This is how React Native types works, and you can see the same behavior with StyleSheet.create.
 
 Now, let's create another variant, e.g., Heading:
 

docs/src/content/docs/start/setup.mdx

@@ -37,7 +37,7 @@ import Seo from '../../../components/Seo.astro'
         lg: 8,
         xl: 12
       }
-    }
+    } as const
     ```
 
     or something more advanced with nested objects / functions:
@@ -76,9 +76,11 @@ import Seo from '../../../components/Seo.astro'
           return `rgba(${rgb.at(0)}, ${rgb.at(1)}, ${rgb.at(2)}, ${opacity})`
         }
       }
-    }
+    } as const
     ```
 
+    It's good to add "as const" to the end of your theme object to make sure TypeScript knows it's a constant object and not a mutable one. It also allows you to spread your partial theme object into a full theme object without TypeScript complaining.
+
     ### Create breakpoints
 
     There are no predefined breakpoints. You can name them anything. Just make an object with string keys and number values.
@@ -93,9 +95,11 @@ import Seo from '../../../components/Seo.astro'
         xl: 1200,
         superLarge: 2000,
         tvLike: 4000
-    }
+    } as const
     ```
 
+    It's good to add "as const" to the end of your breakpoints object to make sure TypeScript knows it's a constant object and not a mutable one.
+
     ### Wrap your app with UnistylesTheme to inject theme
 
     ```tsx