refactor: png を webp に置き換え

_includes/footer.html

@@ -1,6 +1,6 @@
 <footer class="site-footer">
   <div class="footer-logo">
-    <img src="/img/2025/common/footer-logo.png" alt="DojoCon Japan 2025 Inspire Next." />
+    <img src="/img/2025/common/footer-logo.webp" alt="DojoCon Japan 2025 Inspire Next." />
   </div>
   <div class="footer-social">
     <a href="https://x.com/{{ site.x }}" target="_blank" rel="noopener" class="social-x" aria-label="X">

_includes/header.html

@@ -1,5 +1,5 @@
 <h1 class="max-w-lg mx-auto pt-5 px-8">
   <a href="/">
-    <img src="/img/2025/common/header-logo.png" alt="DojoCon Japan 2025 Inspire Next." />
+    <img src="/img/2025/common/header-logo.webp" alt="DojoCon Japan 2025 Inspire Next." />
   </a>
 </h1>

_includes/top/sections/hero.html

@@ -1,5 +1,5 @@
 <div class="max-w-[1500px] mt-2 xl:-mt-14 mx-auto px-[2%] md:px-8">
-  <img src="/img/2025/top/hero-image.png" alt="好奇心に火をつけよう！！ Inspire Next" />
+  <img src="/img/2025/top/hero-image.webp" alt="好奇心に火をつけよう！！ Inspire Next" />
 </div>
 
 <div class="flex mx-auto max-w-[1080px] justify-center lg:justify-start">

index.md

@@ -1,7 +1,7 @@
 ---
 layout: top
 ---
-<div class="bg-[url(/img/2025/top/header-background.png)] bg-contain bg-no-repeat bg-top bg-center">
+<div class="bg-[url(/img/2025/top/header-background.webp)] bg-contain bg-no-repeat bg-top bg-center">
   {% include header.html %}
 
   {% include top/sections/hero.html %}