docs: added openllmetry observability (#369)

apps/docs/docs/modules/observability/_category_.yml

+label: Observability

apps/docs/docs/modules/observability/index.md

+# Observability
+
+LlamaIndex provides **one-click observability** 🔭 to allow you to build principled LLM applications in a production setting.
+
+A key requirement for principled development of LLM applications over your data (RAG systems, agents) is being able to observe, debug, and evaluate
+your system - both as a whole and for each component.
+
+This feature allows you to seamlessly integrate the LlamaIndex library with powerful observability/evaluation tools offered by our partners.
+Configure a variable once, and you'll be able to do things like the following:
+
+- View LLM/prompt inputs/outputs
+- Ensure that the outputs of any component (LLMs, embeddings) are performing as expected
+- View call traces for both indexing and querying
+
+Each provider has similarities and differences. Take a look below for the full set of guides for each one!
+
+## OpenLLMetry
+
+[OpenLLMetry](https://github.com/traceloop/openllmetry-js) is an open-source project based on OpenTelemetry for tracing and monitoring
+LLM applications. It connects to [all major observability platforms](https://www.traceloop.com/docs/openllmetry/integrations/introduction) and installs in minutes.
+
+### Usage Pattern
+
+```bash
+npm install @traceloop/node-server-sdk
+```
+
+```js
+import * as traceloop from "@traceloop/node-server-sdk";
+
+traceloop.initialize({
+  apiKey: process.env.TRACELOOP_API_KEY,
+  disableBatch: true,
+});
+```