Add langchain, marked, and html-entities as dependencies

Several new modules including 'html-entities', 'langchain', 'marked', '@anthropic-ai/sdk' and '@langchain' packages have been added to the project dependencies. This commit also incorporates additions of '@types' modules relevant to the new dependencies.

README.md

@@ -2,7 +2,8 @@
 
 # Opticat
 
-Opticat is an experimental API designed for game development.
+Opticat is an experimental API designed for game development. Currently, it's focusing on text-based role-playing 
+games using LLM(Large Language Model)s, but it may change in the future.
 
 ## Project Status
 
@@ -11,7 +12,7 @@ programming paradigms, it's purely experimental at this point and not suitable f
 
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-| ![Statements](https://img.shields.io/badge/statements-97.71%25-brightgreen.svg?style=flat) | ![Branches](https://img.shields.io/badge/branches-97.77%25-brightgreen.svg?style=flat) | ![Functions](https://img.shields.io/badge/functions-87.23%25-yellow.svg?style=flat) | ![Lines](https://img.shields.io/badge/lines-97.71%25-brightgreen.svg?style=flat) |
+| ![Statements](https://img.shields.io/badge/statements-97.58%25-brightgreen.svg?style=flat) | ![Branches](https://img.shields.io/badge/branches-97.52%25-brightgreen.svg?style=flat) | ![Functions](https://img.shields.io/badge/functions-87.32%25-yellow.svg?style=flat) | ![Lines](https://img.shields.io/badge/lines-97.58%25-brightgreen.svg?style=flat) |
 
 ## Motivation