Added release notes (#3660)

### What problem does this PR solve?


### Type of change


- [x] Documentation Update

docs/release_notes.md

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+---
+sidebar_position: 2
+slug: /release_notes
+---
+
+# Release notes
+
+Key features and improvements in the latest releases.
+
+## v0.14.0
+
+Released on November 26, 2024.
+
+### New features
+
+- Supports [Infinity](https://github.com/infiniflow/infinity) or Elasticsearch (default) as document engine for vector storage and full-text indexing.
+- Enhances user experience by adding more variables to the Agent and implementing auto-saving.
+- Adds a three-step translation agent template, inspired by [Andrew Ng's translation agent](https://github.com/andrewyng/translation-agent).
+- Adds an SEO-optimized blog writing agent template.
+- Provides HTTP and Python APIs for conversing with an agent.
+- Supports the use of English synonyms during retrieval processes.
+- Optimizes term weight calculations, reducing the retrieval time by 50%.
+- Improves task executor monitoring with additional performance indicators.
+- Replaces Redis with Valkey.
+- Adds three new UI languages (contributed by community): Indonesian, Spanish, and Vietnamese.
+
+### Related APIs
+
+#### HTTP APIs
+
+- [Create session with agent](https://ragflow.io/docs/dev/http_api_reference#create-session-with-an-agent)
+- [Converse with agent](https://ragflow.io/docs/dev/http_api_reference#converse-with-agent)
+
+#### Python APIs
+
+- [Create session with agent](https://ragflow.io/docs/dev/python_api_reference#create-session-with-agent)
+- [Converse with agent](https://ragflow.io/docs/dev/python_api_reference#create-session-with-agent)