convert into Hugo module theme

static/js/lazy-images.js

@@ -0,0 +1,49 @@
+// Source: https://css-tricks.com/the-complete-guide-to-lazy-loading-images/
+document.addEventListener("DOMContentLoaded", function() {
+    var lazyloadImages;
+
+    if ("IntersectionObserver" in window) {
+        lazyloadImages = document.querySelectorAll(".lazy");
+        var imageObserver = new IntersectionObserver(function(entries, observer) {
+        entries.forEach(function(entry) {
+            if (entry.isIntersecting) {
+            var image = entry.target;
+            image.classList.remove("lazy");
+            imageObserver.unobserve(image);
+            }
+        });
+        });
+
+        lazyloadImages.forEach(function(image) {
+        imageObserver.observe(image);
+        });
+    } else {
+        var lazyloadThrottleTimeout;
+        lazyloadImages = document.querySelectorAll(".lazy");
+
+        function lazyload () {
+        if(lazyloadThrottleTimeout) {
+            clearTimeout(lazyloadThrottleTimeout);
+        }
+
+        lazyloadThrottleTimeout = setTimeout(function() {
+            var scrollTop = window.pageYOffset;
+            lazyloadImages.forEach(function(img) {
+                if(img.offsetTop < (window.innerHeight + scrollTop)) {
+                img.src = img.dataset.src;
+                img.classList.remove('lazy');
+                }
+            });
+            if(lazyloadImages.length == 0) {
+            document.removeEventListener("scroll", lazyload);
+            window.removeEventListener("resize", lazyload);
+            window.removeEventListener("orientationChange", lazyload);
+            }
+        }, 20);
+        }
+
+        document.addEventListener("scroll", lazyload);
+        window.addEventListener("resize", lazyload);
+        window.addEventListener("orientationChange", lazyload);
+    }
+});