feat: Add UnstructuredOrgModeLoader (#6842)

### Summary

Adds `UnstructuredOrgModeLoader` for processing
[Org-mode](https://en.wikipedia.org/wiki/Org-mode) documents.

### Testing

```python
from langchain.document_loaders import UnstructuredOrgModeLoader

loader = UnstructuredOrgModeLoader(
    file_path="example_data/README.org", mode="elements"
)
docs = loader.load()
print(docs[0])
```

### Reviewers

- @rlancemartin
- @eyurtsev
- @hwchase17

docs/extras/modules/data_connection/document_loaders/integrations/example_data/README.org

@@ -0,0 +1,27 @@
+* Example Docs
+
+The sample docs directory contains the following files:
+
+-  ~example-10k.html~ - A 10-K SEC filing in HTML format
+-  ~layout-parser-paper.pdf~ - A PDF copy of the layout parser paper
+-  ~factbook.xml~ / ~factbook.xsl~ - Example XML/XLS files that you
+   can use to test stylesheets
+
+These documents can be used to test out the parsers in the library. In
+addition, here are instructions for pulling in some sample docs that are
+too big to store in the repo.
+
+** XBRL 10-K
+
+You can get an example 10-K in inline XBRL format using the following
+~curl~. Note, you need to have the user agent set in the header or the
+SEC site will reject your request.
+
+#+BEGIN_SRC bash
+
+   curl -O \
+     -A '${organization} ${email}'
+     https://www.sec.gov/Archives/edgar/data/311094/000117184321001344/0001171843-21-001344.txt
+#+END_SRC
+
+You can parse this document using the HTML parser.

docs/extras/modules/data_connection/document_loaders/integrations/org_mode.ipynb

@@ -0,0 +1,88 @@
+{
+ "cells": [
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "# Org-mode\n",
+    "\n",
+    ">A [Org Mode document](https://en.wikipedia.org/wiki/Org-mode) is a document editing, formatting, and organizing mode, designed for notes, planning, and authoring within the free software text editor Emacs."
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## `UnstructuredOrgModeLoader`\n",
+    "\n",
+    "You can load data from Org-mode files with `UnstructuredOrgModeLoader` using the following workflow."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 1,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "from langchain.document_loaders import UnstructuredOrgModeLoader"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 2,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "loader = UnstructuredOrgModeLoader(\n",
+    "    file_path=\"example_data/README.org\", mode=\"elements\"\n",
+    ")\n",
+    "docs = loader.load()"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 3,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "page_content='Example Docs' metadata={'source': 'example_data/README.org', 'filename': 'README.org', 'file_directory': 'example_data', 'filetype': 'text/org', 'page_number': 1, 'category': 'Title'}\n"
+     ]
+    }
+   ],
+   "source": [
+    "print(docs[0])"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": []
+  }
+ ],
+ "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": "3.8.13"
+  }
+ },
+ "nbformat": 4,
+ "nbformat_minor": 4
+}