add version number to cache names

meta/sw.js.njk

@@ -4,6 +4,8 @@ eleventyExcludeFromCollections: true
 ---
 importScripts('https://storage.googleapis.com/workbox-cdn/releases/3.6.1/workbox-sw.js');
 
+const _version = '-1';
+
 if (workbox) {
     workbox.precaching.precacheAndRoute([]);
 
@@ -35,7 +37,7 @@ if (workbox) {
         // Cache CSS files
         /.*\.css/,
         workbox.strategies.staleWhileRevalidate({
-            cacheName: 'css-cache',
+            cacheName: 'css-cache' + _version,
         })
     );
 
@@ -43,7 +45,7 @@ if (workbox) {
         // Cache image files
         /.*\.(?:png|jpg|jpeg|svg|gif)/,
         workbox.strategies.cacheFirst({
-            cacheName: 'image-cache',
+            cacheName: 'image-cache' + _version,
             plugins: [
                 new workbox.expiration.Plugin({
                     maxEntries: 100,