Add Acreom Document Loader to LangChain JS for Feature Parity with LangChain Python

[SkSirius]

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Feature request

Introduce an Acreom document loader to LangChain JS, mirroring the functionality available in LangChain Python. This loader should handle .md files, including processing front matter, custom Acreom-specific rules, and metadata extraction.

Motivation

The Acreom loader is an essential feature for users who work extensively with Acreom markdown files. Adding this to LangChain JS will:

1.	Ensure feature parity with the Python implementation, enhancing the consistency of the LangChain ecosystem.
2.	Provide JS/TS developers with robust support for Acreom documents without needing external or custom solutions.

Proposal (If applicable)

Pull Request: #7525