Use fully qualified markitdown imports

[deepdive101]

I installed markitdown directly from GitHub using the command uv add git+https://github.com/microsoft/markitdown. I did this because the GitHub version contains unreleased changes that I require.

I ran into two import errors caused by these lines in __main__.py:

from __about__ import __version__
from _markitdown import MarkItDown, DocumentConverterResult

To address these two import errors, I had to change the above two lines in __main__.py to use fully qualified imports:

from markitdown.__about__ import __version__
from markitdown._markitdown import MarkItDown, DocumentConverterResult

I request that __main__.py be updated in this way to prevent the import errors.

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For your reference, the tracebacks were:

Traceback (most recent call last):
  File "/projects/doc-convert/./.venv/bin/markitdown", line 4, in <module>
    from markitdown.__main__ import main
  File "/projects/doc-convert/.venv/lib64/python3.11/site-packages/markitdown/__main__.py", line 7, in <module>
    from __about__ import __version__
ModuleNotFoundError: No module named '__about__'

Traceback (most recent call last):
  File "/projects/doc-convert/./.venv/bin/markitdown", line 4, in <module>
    from markitdown.__main__ import main
  File "/projects/doc-convert/.venv/lib64/python3.11/site-packages/markitdown/__main__.py", line 8, in <module>
    from _markitdown import MarkItDown, DocumentConverterResult
ModuleNotFoundError: No module named '_markitdown'