Comment map more fully (#1100)

Comments are good.

Author: willum070

samples/circle-simple/index.ts

@@ -9,7 +9,6 @@ const mapElement = document.querySelector('gmp-map') as google.maps.MapElement;
 let innerMap;
 
 async function initMap() {
-    // Import the needed libraries.
     // Request needed libraries.
     (await google.maps.importLibrary('maps')) as google.maps.MapsLibrary;
     (await google.maps.importLibrary('marker')) as google.maps.MarkerLibrary;
@@ -18,13 +17,16 @@ async function initMap() {
         'gmp-map'
     ) as google.maps.MapElement;
 
+    // Set the initial map center point.
     const initialCenter = { lat: 34.98956821576194, lng: 135.74239981260283 }; // Hotel Emion, Kyoto, Japan
 
     // Get the inner map.
     const innerMap = mapElement.innerMap;
 
+    // Get the buttons.
     const buttons = document.querySelectorAll('input[name="radius"]');
 
+    // Create the circle.
     const walkingCircle = new google.maps.Circle({
         strokeColor: '#ffdd00ff',
         strokeOpacity: 0.8,