Feature/add acreom loader (#5780)

adding new loader for [acreom](https://acreom.com) vaults. It's based on
the Obsidian loader with some additional text processing for acreom
specific markdown elements.

 @eyurtsev please take a look!

---------

Co-authored-by: rlm <pexpresss31@gmail.com>

docs/modules/indexes/document_loaders/examples/acreom.ipynb

@@ -0,0 +1,75 @@
+{
+ "cells": [
+  {
+   "cell_type": "markdown",
+   "id": "e310c8dc-acd0-48d2-801c-f37ce99acd2d",
+   "metadata": {},
+   "source": [
+    "# acreom"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "04a2c95d-4114-431e-904a-32d79005c28b",
+   "metadata": {},
+   "source": [
+    "[acreom](https://acreom.com) is a dev-first knowledge base with tasks running on local markdown files.\n",
+    "\n",
+    "Below is an example on how to load a local acreom vault into Langchain. As the local vault in acreom is a folder of plain text .md files, the loader requires the path to the directory. \n",
+    "\n",
+    "Vault files may contain some metadata which is stored as a YAML header. These values will be added to the document’s metadata if `collect_metadata` is set to true. "
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "0169bee5-aa7a-4ec7-b7e7-b3bb2e58f3bb",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "from langchain.document_loaders import AcreomLoader"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "c1b49ab3-616b-4149-bef5-7559d65d3d2b",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "loader = AcreomLoader('<path-to-acreom-vault>', collect_metadata=False)"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "3127a018-9c1c-4886-8321-f5666d970a95",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "docs = loader.load()"
+   ]
+  }
+ ],
+ "metadata": {
+  "kernelspec": {
+   "display_name": "Python 3 (ipykernel)",
+   "language": "python",
+   "name": "python3"
+  },
+  "language_info": {
+   "codemirror_mode": {
+    "name": "ipython",
+    "version": 3
+   },
+   "file_extension": ".py",
+   "mimetype": "text/x-python",
+   "name": "python",
+   "nbconvert_exporter": "python",
+   "pygments_lexer": "ipython3",
+   "version": "3.10.10"
+  }
+ },
+ "nbformat": 4,
+ "nbformat_minor": 5
+}