feat: detect language for PDFs

[shreyanid]

The @apply_metadata decorator already contains logic to detect the language of the element text (on either a document or element level). Update pdfs, and later images, to use this decorator to get accurate element language results outputted.

Test

from unstructured.partition.auto import partition

def test_partition_pdf():
    pdf_path = "example-docs/language-docs/fr_olap.pdf"
    elements = partition(pdf_path)  # optionally set `detect_language_per_element=True)`
    print(f"Number of elements partitioned: {len(elements)}")

    # Check if elements are returned
    assert len(elements) > 0, "No elements were partitioned from the PDF."

    # check language outputted for each element
    for element in elements:
        print(element)
        print(element.metadata.languages)
        print("-------------------------------")

test_partition_pdf()