feat: migrate to esm

frontend/app/scripts/accumulate-licenses.ts

@@ -13,8 +13,8 @@
  * this program. If not, see <https://www.gnu.org/licenses/>.
  */
 import fs from 'fs';
-import {omit} from '../src/app/_helpers/collections/omit';
-import {pickBy} from '../src/app/_helpers/collections/pick';
+import {omit} from '../src/app/_helpers/collections/omit.js';
+import {pickBy} from '../src/app/_helpers/collections/pick.js';
 
 /**
  * accumulate and transform licenses based on two license files

frontend/app/scripts/check-icon-correctness.ts

@@ -15,7 +15,7 @@
 import fontkit, {Font} from 'fontkit';
 import config from '../icons.config';
 import {existsSync} from 'fs';
-import {getUsedIconsHtml, getUsedIconsTS} from './gather-used-icons';
+import {getUsedIconsHtml, getUsedIconsTS} from './gather-used-icons.js';
 
 const commandName = '"npm run minify-icons"';
 const originalFont = fontkit.openSync(config.inputPath);

frontend/app/scripts/gather-used-icons.ts

@@ -14,7 +14,7 @@
  */
 import glob from 'glob';
 import {readFileSync} from 'fs';
-import {matchPropertyContent, matchTagProperties} from '../src/app/util/ion-icon/icon-match';
+import {matchPropertyContent, matchTagProperties} from '../src/app/util/ion-icon/icon-match.js';
 
 const globPromise = (pattern: string) =>
   new Promise<string[]>((resolve, reject) =>

frontend/app/scripts/minify-icon-font.ts

@@ -18,7 +18,7 @@ import fontkit from 'fontkit';
 import {exec} from 'child_process';
 import config from '../icons.config';
 import {statSync} from 'fs';
-import {getUsedIconsHtml, getUsedIconsTS} from './gather-used-icons';
+import {getUsedIconsHtml, getUsedIconsTS} from './gather-used-icons.js';
 
 /**
  *