Fixed types and docs for recognize parameters per #856

[cpruijsen]

Summary

• Type RecognizeOptions as extending WorkerParams so Tesseract parameters can be passed to worker.recognize and scheduler.addJob('recognize', ...) without a type error (Fix types for setting Tesseract parameters in recognize #856).
• Document that those parameters apply to a single job and are restored afterwards (unlike worker.setParameters).
• Allow tessedit_pageseg_mode: "6" as well as PSM.SINGLE_BLOCK, matching the issue snippet.

Per-job parameters have been supported at runtime since v4 (#665): src/worker-script/index.js already splits options into Tesseract.js keys and pass-through SetVariable calls, then RestoreParameters. scheduler.addJob('recognize') is typed as Parameters<Worker['recognize']>, so fixing RecognizeOptions fixes the scheduler call site in the issue.

What I chose and the alternative

• Chose RecognizeOptions extends WorkerParams. Alternative: only add [propName: string]: any on RecognizeOptions. That would silence the excess-property error but would not autocomplete tessedit_*. Happy to switch.
• Chose tessedit_pageseg_mode: PSM | \${PSM}`. Alternative: keep PSMand require the enum member. The issue example uses"6"`, which TypeScript string enums reject. Happy to drop the union.

Test plan

• scheduler.addJob('recognize', image, { tessedit_pageseg_mode: "6" }) typechecks
• worker.recognize(image, { tessedit_pageseg_mode: PSM.SINGLE_BLOCK }) typechecks
• worker.recognize(image, { tessedit_char_whitelist: 'Tess', rectangle: { ... } }) typechecks
• worker.recognize with tessedit_char_whitelist in options returns the filtered text, and the next job without that option returns the full text
• Karma / full npm test (Chrome + Firefox), not run in this change; Node mocha only

Fixes #856