Cleanup and refactor, in preparation for plugin support. (#318)

* Work started moving converters to individual files.
* Significant cleanup and refactor.
* Moved everything to a packages subfolder.
* Added sample plugin.
* Added instructions to the README.md
* Bumped version, and added a note about compatibility.

packages/markitdown-sample-plugin/tests/test_sample_plugin.py

@@ -0,0 +1,40 @@
+#!/usr/bin/env python3 -m pytest
+import os
+import pytest
+
+from markitdown import MarkItDown
+from markitdown_sample_plugin import RtfConverter
+
+TEST_FILES_DIR = os.path.join(os.path.dirname(__file__), "test_files")
+
+RTF_TEST_STRINGS = {
+    "This is a Sample RTF File",
+    "It is included to test if the MarkItDown sample plugin can correctly convert RTF files.",
+}
+
+
+def test_converter() -> None:
+    """Tests the RTF converter dirctly."""
+    converter = RtfConverter()
+    result = converter.convert(
+        os.path.join(TEST_FILES_DIR, "test.rtf"), file_extension=".rtf"
+    )
+
+    for test_string in RTF_TEST_STRINGS:
+        assert test_string in result.text_content
+
+
+def test_markitdown() -> None:
+    """Tests that MarkItDown correctly loads the plugin."""
+    md = MarkItDown()
+    result = md.convert(os.path.join(TEST_FILES_DIR, "test.rtf"))
+
+    for test_string in RTF_TEST_STRINGS:
+        assert test_string in result.text_content
+
+
+if __name__ == "__main__":
+    """Runs this file's tests from the command line."""
+    test_converter()
+    test_markitdown()
+    print("All tests passed.")