Run Tailwind CSS from installed plugin directory

Workaround to address an error, possibly related to Tailwind CSS 4.x:

npm error could not determine executable to run

pelican/plugins/tailwindcss/tailwindcss.py

@@ -65,9 +65,8 @@ def generate_css(po):
     input_output = f"-i {input_file_path} -o {output_file_path}"
     print(f"{utils.LOG_PREFIX} Build css ({output_file_path})")
 
-    subprocess.run(
+    commands.run_in_plugin(
         f"npx tailwindcss -c {twconfig_file_path} {input_output}",
-        shell=True,
     )