refactor: convert contentScriptsUtils to Typescript

Change-Id: I78031a291a34198ac6335a4ee42eb23753f2c37b
diff --git a/src/contentScripts/publicThreadStart.js b/src/contentScripts/publicThreadStart.js
index a95485b..40cd302 100644
--- a/src/contentScripts/publicThreadStart.js
+++ b/src/contentScripts/publicThreadStart.js
@@ -1,4 +1,4 @@
-import {injectStylesheet} from '../common/contentScriptsUtils.js';
+import {injectStylesheet} from '../common/contentScriptsUtils';
 import {getOptions} from '../common/options/optionsUtils.js';
 import {setUpRedirectIfEnabled} from '../redirect/setup.js';