run npm cache clean

src/install-plugin.ts

@@ -132,6 +132,8 @@ async function main() {
     logger.warn(`No plugins found, exiting.`);
     return;
   }
+  logger.info(`Cleaning NPM cache.`);
+  await execAsync(`npm cache clean --force`);
   for (const [name, info] of Object.entries(plugins)) {
     if (!info.$install) {
       continue;