Feat: add comments for the changes as requested

Author: rawalyogendra

packages/react-native-web/src/exports/Dimensions/index.js

@@ -80,6 +80,13 @@ export default class Dimensions {
     let height;
     let width;
 
+    /*
+     * iOS does not update viewport dimensions on keyboard open/close
+     * So, we are using window.visualViewport(https://developer.mozilla.org/en-US/docs/Web/API/VisualViewport)
+     * instead of document.documentElement.clientHeight
+     * But we are still using document.documentElement.clientWidth as fallback
+     * because it was requested by the original repo owner
+     */
     if (win.visualViewport) {
       const visualViewport = win.visualViewport;
       height = Math.round(visualViewport.height);
@@ -136,6 +143,10 @@ export default class Dimensions {
 }
 
 if (canUseDOM) {
+  /*
+   * Same here as in _update method
+   * keeping the previous implementation as fallback
+   */
   if (window.visualViewport) {
     window.visualViewport.addEventListener('resize', Dimensions._update, false);
   } else {