Update (primarily) the Node.js examples to release page resources

Given that Node.js doesn't support Workers, general PDF.js performance will be worse when compared to browsers. In an attempt to improve at least memory usage a little bit, update the Node.js examples to release page resources once parsing is done for that page.

examples/node/getinfo.js

@@ -53,6 +53,8 @@ loadingTask.promise
             });
             console.log("## Text Content");
             console.log(strings.join(" "));
+            // Release page resources.
+            page.cleanup();
           })
           .then(function () {
             console.log();

examples/node/pdf2png/pdf2png.js

@@ -103,6 +103,8 @@ const loadingTask = pdfjsLib.getDocument({
         );
       }
     });
+    // Release page resources.
+    page.cleanup();
   } catch (reason) {
     console.log(reason);
   }

examples/node/pdf2svg.js

@@ -118,6 +118,8 @@ const loadingTask = pdfjsLib.getDocument({
       svgGfx.embedFonts = true;
       const svg = await svgGfx.getSVG(opList, viewport);
       await writeSvgToFile(svg, getFilePathForPage(pageNum));
+      // Release page resources.
+      page.cleanup();
     } catch (err) {
       console.log(`Error: ${err}`);
     }

examples/text-only/pdf2svg.js

@@ -58,6 +58,8 @@ async function pageLoaded() {
   // building SVG and adding that to the DOM
   const svg = buildSVG(viewport, textContent);
   document.getElementById("pageContainer").appendChild(svg);
+  // Release page resources.
+  page.cleanup();
 }
 
 document.addEventListener("DOMContentLoaded", function () {