new utility - OCR a scanned PDF

### Description of the new feature / enhancement

Extension for Windows Explorer Context menu (right click) for PDF files (images, scans):

- OCR the PDF (add a text layer)
- save the PDF (either override or Save as ...)

Should work on a single PDF file, on all the selected PDF files.
Maybe an option for "all PDF files in a folder" ?

If a PDF already contains a text layer (i.e. it is not a scanned image PDF), nothing needs to be done.

### Scenario when this would be used?

For

- a self employed person (consultant, sales, developer, ...)
- home offices
- small offices

there is usually some multifunction scanner, but no document management systems with OCR.
The scanned documents are usually collected as non-searchable PDF files, containing images and no (searchable) text layer.
To make them searchable, I have to open the PDF tool, perform an OCR, and save the file (usually to a new file name).

Doing OCR on a PDF and saving it with a single context menu selection could make this process much less time-consuming ...

### Supporting information

Powertoys already has an OCR function for on-screen OCR.
This could be used on the image in the PDF.
So we need to add the text layer (from the OCR) to the PDF and save it.

I am a C# developer; could assist implementing this feature.

No implementation files or tests are named. Start by locating PowerToys' existing on-screen OCR function and the Windows Explorer PDF context-menu integration, then determine how PDF text layers can be created and saved. Done means OCR works for selected PDF files, leaves PDFs with existing text unchanged, and supports the intended save behavior.

Written by the indexing model from the issue text.