fix: use getInput for github_token instead of process.env

Properly access github_token input using the getInput helper function
from io.ts instead of directly accessing process.env.

Co-authored-by: EndBug <26386270+EndBug@users.noreply.github.com>

Author: Copilot

lib/index.js

@@ -3,11 +3,12 @@ import * as core from '@actions/core';
 import * as YAML from 'js-yaml';
 import {getOctokit} from '@actions/github';
 import * as fs from 'fs';
+import {getInput} from './io';
 
 function getOctokitClient() {
-  const token = process.env.INPUT_GITHUB_TOKEN;
+  const token = getInput('github_token');
   if (!token) {
-    throw new Error('GITHUB_TOKEN is required');
+    throw new Error('github_token is required');
   }
   return getOctokit(token);
 }