fix: og:image doesn't support relative paths

Author: ludgie

src/template_pre.html

@@ -9,7 +9,7 @@
 <!-- Open Graph protocol -->
 <meta property="og:title" content="labwc" />
 <meta property="og:type" content="website" />
-<meta property="og:image" content="img/labwc2-with-text.png" />
+<meta property="og:image" content="https://labwc.github.io/img/labwc2-with-text.png" />
 <meta property="og:url" content="https://labwc.github.io" />
 <meta property="og:description" content="An Openbox inspired wlroots-based stacking Wayland compositor." />
 <style>