Add srcset for yosemite portrait, limited resolutions

The image is not very high quality, and it compresses badly, making
larger than desired file sizes required to have any kind of visual
quality. Probably will change the picture.

2023/index.html

@@ -26,7 +26,25 @@ <h1>Pieter Gijsbers</h1>
     <a href="about.html" class="box about-tile">
         <div class="overlay"></div>
         <h1 class="tile-text upper-case">about</h1>
-        <img class="tile" src="img/me-ar-2-1-q15.jpg" alt="Go to about page">
+        <picture>
+            <source
+                    type="image/avif"
+                    srcset="img/landscape/pieter_halfdome-640-q28.avif 640w,
+                            img/landscape/pieter_halfdome-960-q20.avif 960w,
+                            img/landscape/pieter_halfdome-1920-q20.avif 1920w,
+                            img/landscape/pieter_halfdome-3840-q25.avif 38400w"
+            />
+            <source
+                    type="image/jpg"
+                    srcset="img/landscape/pieter_halfdome-960-q30.jpg 960w,
+                            img/landscape/pieter_halfdome-1920-q30.jpg 1920w"
+            />
+            <img class="tile"
+                src="img/landscape/pieter_halfdome-1920-q30.jpg"
+                alt="Go to about page"
+                sizes="(max-width: 500px) 80vw, 50vw"
+            >
+        </picture>
     </a>
     <a href="https://scholar.google.com/citations?hl=en&user=Za3OsTwAAAAJ"
        class="box">