card: add top image attributes for lazy loading

examples/official-site/sqlpage/migrations/31_card_docs_update.sql

@@ -18,6 +18,9 @@ INSERT INTO parameter(component, name, description, type, top_level, optional) S
         This is useful if you want to display a lot of text in the card, with many options for formatting, such as
         line breaks, **bold**, *italics*, lists, #titles, [links](target.sql), ![images](photo.jpg), etc.', 'TEXT', FALSE, TRUE),
     ('top_image', 'The URL (absolute or relative) of an image to display at the top of the card.', 'URL', FALSE, TRUE),
+    ('top_image_lazy', 'Whether the top image must be lazily loaded. Defaults to false, meaning eagerly loaded.', 'BOOLEAN', FALSE, TRUE),
+    ('top_image_width', 'Specify the top image width, in pixels. Helps prevent layout shifts.', 'INTEGER', FALSE, TRUE),
+    ('top_image_height', 'Specify the top image height, in pixels. Helps prevent layout shifts.', 'INTEGER', FALSE, TRUE),
     ('footer', 'Muted text to display at the bottom of the card.', 'TEXT', FALSE, TRUE),
     ('footer_md', 'Muted text to display at the bottom of the card, with rich text formatting in Markdown format.', 'TEXT', FALSE, TRUE),
     ('link', 'An URL to which the user should be taken when they click on the card.', 'URL', FALSE, TRUE),
@@ -58,9 +61,9 @@ INSERT INTO example(component, description, properties) VALUES
     ('card', 'A gallery of images.',
         json('[
             {"component":"card", "title":"My favorite animals in pictures", "columns": 3},
-            {"title": "Lynx", "description_md": "The **lynx** is a medium-sized **wild cat** native to Northern, Central and Eastern Europe to Central Asia and Siberia, the Tibetan Plateau and the Himalayas.", "top_image": "https://upload.wikimedia.org/wikipedia/commons/thumb/d/d8/Lynx_lynx-4.JPG/640px-Lynx_lynx-4.JPG", "icon":"star" },
-            {"title": "Squirrel", "description_md": "The **chipmunk** is a small, striped rodent of the family Sciuridae. Chipmunks are found in North America, with the exception of the Siberian chipmunk which is found primarily in Asia.", "top_image": "https://upload.wikimedia.org/wikipedia/commons/thumb/b/be/Tamias-rufus-001.jpg/640px-Tamias-rufus-001.jpg" },
-            {"title": "Spider", "description_md": "The **jumping spider family** (_Salticidae_) contains more than 600 described genera and about *6000 described species*, making it the largest family of spiders with about 13% of all species.", "top_image": "https://upload.wikimedia.org/wikipedia/commons/thumb/a/ab/Jumping_spiders_%28Salticidae%29.jpg/640px-Jumping_spiders_%28Salticidae%29.jpg" }
+            {"title": "Lynx", "description_md": "The **lynx** is a medium-sized **wild cat** native to Northern, Central and Eastern Europe to Central Asia and Siberia, the Tibetan Plateau and the Himalayas.", "top_image": "https://upload.wikimedia.org/wikipedia/commons/thumb/3/3a/Lynx_lynx_-_05.jpg/330px-Lynx_lynx_-_05.jpg", "top_image_width": 330, "top_image_height": 495, "top_image_lazy": true, "icon":"star" },
+            {"title": "Squirrel", "description_md": "The **chipmunk** is a small, striped rodent of the family Sciuridae. Chipmunks are found in North America, with the exception of the Siberian chipmunk which is found primarily in Asia.", "top_image": "https://upload.wikimedia.org/wikipedia/commons/thumb/4/4a/American_squirrel_eating_nut%2C_13_Jun_2013.JPG/330px-American_squirrel_eating_nut%2C_13_Jun_2013.JPG", "top_image_width": 330, "top_image_height": 495, "top_image_lazy": true },
+            {"title": "Spider", "description_md": "The **jumping spider family** (_Salticidae_) contains more than 600 described genera and about *6000 described species*, making it the largest family of spiders with about 13% of all species.", "top_image": "https://upload.wikimedia.org/wikipedia/commons/thumb/0/0f/Australian_orb_weaver_spinning_web.jpg/330px-Australian_orb_weaver_spinning_web.jpg", "top_image_width": 330, "top_image_height": 495, "top_image_lazy": true }
         ]')),
     ('card', 'Beautifully colored cards with variable width. The blue card (width 6) takes half the screen, whereas of the red and green cards have the default width of 3',
         json('[

sqlpage/templates/card.handlebars

@@ -38,7 +38,7 @@
                     <a href="{{link}}" style="text-decoration: inherit; color: inherit">
                 {{/if}}
                 {{#if top_image}}
-                    <img src="{{top_image}}" class="card-img-top" />
+                    <img src="{{top_image}}" class="card-img-top"{{#if top_image_width}} width="{{top_image_width}}"{{/if}}{{#if top_image_height}} height="{{top_image_height}}"{{/if}}{{#if top_image_lazy}} loading="lazy"{{/if}}/>
                 {{/if}}
                 {{#if color}}
                     {{#if (not embed)}}