docs: add links to source

Author: atinux

docs/content/2.usage/1.nuxt-img.md

@@ -1,6 +1,11 @@
 ---
 title: '<NuxtImg>'
 description: Discover how to use and configure the Nuxt Image component.
+links:
+  - label: Source
+    icon: i-simple-icons-github
+    to: https://github.com/nuxt/image/blob/main/src/runtime/components/nuxt-img.ts
+    size: xs
 ---
 
 `<NuxtImg>` is a drop-in replacement for the native `<img>` tag.

docs/content/2.usage/2.nuxt-picture.md

@@ -1,6 +1,11 @@
 ---
 title: '<NuxtPicture>'
 description: Discover how to use and configure the Nuxt Picture component.
+links:
+  - label: Source
+    icon: i-simple-icons-github
+    to: https://github.com/nuxt/image/blob/main/src/runtime/components/nuxt-picture.ts
+    size: xs
 ---
 
 `<NuxtPicture>` is a drop-in replacement for the native `<picture>` tag.

docs/content/2.usage/3.use-image.md

@@ -1,6 +1,11 @@
 ---
 title: useImage()
 description: A Vue composable that returns a helper function to generate optimized image URLs.
+links:
+  - label: Source
+    icon: i-simple-icons-github
+    to: https://github.com/nuxt/image/blob/main/src/runtime/composables.ts
+    size: xs
 ---
 
 Sometimes you might need to use a generated image URL directly with applied transformations instead of the `<NuxtImg>` and `<NuxtPicture>` components. This is where `useImage()` comes in (and the helper function it returns, which you will often see referenced directly as `$img` or `img`).