fix: replace PaginatedList slicing with itertools.islice in _extract_issues

PyGithub's PaginatedList slicing (issues[:max_issues]) may fail with
'list index out of range' on some PyGithub versions or when repos
have no issues. Replace with itertools.islice() which works reliably
with any iterable, including PaginatedList.

Bug reported by @dream0438-cmd in PR #269.
Closes #269

src/skill_seekers/cli/github_scraper.py

@@ -16,6 +16,7 @@ Usage:
 
 import argparse
 import fnmatch
+import itertools
 import json
 import logging
 import os
@@ -812,7 +813,7 @@ class GitHubScraper:
             issues = self.repo.get_issues(state="all", sort="updated", direction="desc")
 
             issue_list = []
-            for issue in issues[: self.max_issues]:
+            for issue in itertools.islice(issues, self.max_issues):
                 # Skip pull requests (they appear in issues)
                 if issue.pull_request:
                     continue