added markdown document for ocr engine comparison

[Kaan0029]

ADR for OCR project.
#13313

[jabref-machine]

Note that your PR will not be reviewed/accepted until you have gone through the mandatory checks in the description and marked each of them them exactly in the format of [x] (done), [ ] (not done yet) or [/] (not applicable).

[trag-bot]

@trag-bot didn't find any issues in the code! ✅✨

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You have removed the "Mandatory Checks" section from your pull request description. Please adhere to our pull request template.

[jabref-machine]

You modified Markdown (*.md) files and did not meet JabRef's rules for consistently formatted Markdown files. To ensure consistent styling, we have markdown-lint in place. Markdown lint's rules help to keep our Markdown files consistent within this repository and consistent with the Markdown files outside here.

You can check the detailed error output by navigating to your pull request, selecting the tab "Checks", section "Tests" (on the left), subsection "Markdown".