feat: Add GitHub PR and issue templates for better contributor experience

.github/ISSUE_TEMPLATE/config.yml

@@ -0,0 +1,14 @@
+blank_issues_enabled: true
+contact_links:
+  - name: 📖 Documentation
+    url: https://github.com/LEANN-RAG/LEANN-RAG/tree/main/docs
+    about: Read the documentation for setup and usage instructions
+  - name: 💬 Discord Community
+    url: https://discord.gg/your-discord-link
+    about: Join our Discord for discussions and community support
+  - name: 🤔 Discussions
+    url: https://github.com/LEANN-RAG/LEANN-RAG/discussions
+    about: Ask questions and share ideas with the community
+  - name: 🧪 Benchmark Question
+    url: https://github.com/LEANN-RAG/LEANN-RAG/discussions/categories/benchmarks
+    about: Share or discuss performance benchmarks