Add img.alt= for screenshots

Author: kernc

index.html

@@ -380,16 +380,16 @@ <h4>Use case №1: Find global minimium of an objective/cost function</h4>
            [ 9.998e-01  9.996e-01]]
     funv: [ 1.000e+00  ...  5.210e-08]</code></pre>
         <div class="snippet snippet-plot" data-plot="1: Convergence">
-            <img src="convergence.svg" loading="lazy" />
+            <img src="convergence.svg" alt="Convergence of different algorithms: SHGO, SCE-UA, SMBO" loading="lazy" />
         </div>
         <div class="snippet snippet-plot" data-plot="2: Objective">
-            <img src="objective.svg" loading="lazy" rel="screenshot og:image"/>
+            <img src="objective.svg" loading="lazy" alt="Objective landscape plot" rel="screenshot og:image"/>
         </div>
         <div class="snippet snippet-plot" data-plot="3: Evaluations">
-            <img src="evaluations.svg" loading="lazy" />
+            <img src="evaluations.svg" alt="Sequence of evaluations plot" loading="lazy" />
         </div>
         <div class="snippet snippet-plot" data-plot="4: Regret">
-            <img src="regret.svg" loading="lazy" />
+            <img src="regret.svg" alt="Cumulative regret plot" loading="lazy" />
         </div>
     </div>
 
@@ -427,7 +427,7 @@ <h4>Use case №2: Sequential surrogate model-based optimization through "ask-an
 result: OptimizeResult = optimizer.run()
 </code></pre>
         <div class="snippet snippet-plot" data-plot="- SMBO estimators">
-            <img src="convergence2.svg" loading="lazy" />
+            <img src="convergence2.svg" alt="Convergence plot of SMBO estimators" loading="lazy" />
         </div>
     </div>
 
@@ -598,7 +598,7 @@ <h3>Benchmark</h3>
         </script>
     </div>
 </section>
-<img src="contourf.jpg" loading="lazy" style="margin:3em 0 0 0; opacity: .8"/>
+<img src="contourf.jpg" alt="Contour landscapes of benchmarked functions" loading="lazy" style="margin:3em 0 0 0; opacity: .8"/>
 
 <section id="citing">
     <h3>Citation</h3>