Restore caching busting functionality without using explict version number

Fixes #4503

packages/node_modules/@node-red/editor-api/lib/editor/ui.js

@@ -13,6 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  **/
+const crypto = require('crypto')
 var express = require('express');
 var fs = require("fs");
 var path = require("path");
@@ -28,6 +29,8 @@ var editorClientDir = path.dirname(require.resolve("@node-red/editor-client"));
 var defaultNodeIcon = path.join(editorClientDir,"public","red","images","icons","arrow-in.svg");
 var editorTemplatePath = path.join(editorClientDir,"templates","index.mst");
 var editorTemplate;
+const version = require(path.join(editorClientDir,"package.json")).version
+const cacheBuster = crypto.createHash('md5').update(version).digest("hex").substring(0,12)
 
 module.exports = {
     init: function(_runtimeAPI) {
@@ -99,6 +102,7 @@ module.exports = {
         }
         res.send(Mustache.render(editorTemplate,{
             sessionMessages,
+            cacheBuster,
             ...await theme.context()
         }));
     },