docs(README): add new tool descriptions and features overview (#4870)

# Description of Changes

This pull request updates the `README.md` documentation to include
several newly supported PDF operations, making the feature list more
comprehensive and informative for users. The most important changes are
grouped by the type of PDF operation added.

New multi-function and conversion features:

* Added **PDF Multi Tool** to the Organise section, allowing users to
access merge, rotate, rearrange, split, and delete actions from a single
dashboard.
* Added **URL/Website to PDF** to the Convert to PDF section, enabling
users to capture live webpages as PDFs.
* Added **PDF to Video Slideshow** to the Export section, allowing users
to export PDF pages as an automated video presentation.

New extraction and analysis features:

* Added **Extract Attachments** to the Edit & Extract section, making it
possible to retrieve embedded attachments from PDFs.

---

## Checklist

### General

- [ ] I have read the [Contribution
Guidelines](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/CONTRIBUTING.md)
- [ ] I have read the [Stirling-PDF Developer
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/DeveloperGuide.md)
(if applicable)
- [ ] I have read the [How to add new languages to
Stirling-PDF](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/HowToAddNewLanguage.md)
(if applicable)
- [ ] I have performed a self-review of my own code
- [ ] My changes generate no new warnings

### Documentation

- [ ] I have updated relevant docs on [Stirling-PDF's doc
repo](https://github.com/Stirling-Tools/Stirling-Tools.github.io/blob/main/docs/)
(if functionality has heavily changed)
- [ ] I have read the section [Add New Translation
Tags](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/HowToAddNewLanguage.md#add-new-translation-tags)
(for new translation tags only)

### Translations (if applicable)

- [ ] I ran
[`scripts/counter_translation.py`](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/docs/counter_translation.md)

### UI Changes (if applicable)

- [ ] Screenshots or videos demonstrating the UI changes are attached
(e.g., as comments or direct attachments in the PR)

### Testing (if applicable)

- [ ] I have tested my changes locally. Refer to the [Testing
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/DeveloperGuide.md#6-testing)
for more details.

README.md

@@ -33,6 +33,7 @@ All documentation available at [https://docs.stirlingpdf.com/](https://docs.stir
 ### 50+ PDF Operations
 
 #### Organise
+- **PDF Multi Tool**: Access merge, rotate, rearrange, split and delete actions from a single dashboard
 - **Merge**: Combine multiple PDFs into one
 - **Split**: Divide PDFs into multiple files
 - **Extract page(s)**: Extract specific pages from PDF
@@ -47,6 +48,7 @@ All documentation available at [https://docs.stirlingpdf.com/](https://docs.stir
 #### Convert to PDF
 - **Image to PDF**: Convert images to PDF format
 - **Convert file to PDF**: Convert various common file types to PDF
+- **URL/Website to PDF**: Capture live webpages as PDFs
 - **HTML to PDF**: Transform HTML documents to PDF
 - **Markdown to PDF**: Convert Markdown files to PDF
 - **CBZ to PDF**: Convert comic book archives
@@ -68,6 +70,7 @@ All documentation available at [https://docs.stirlingpdf.com/](https://docs.stir
 - **PDF to CBZ**: Convert to comic book archive
 - **PDF to CBR**: Convert to comic book rar archive
 - **PDF to Vector Image**: Convert PDF to vector image (EPS, PS, PCL, XPS) format
+- **PDF to Video Slideshow**: Export pages as an automated video presentation
 
 #### Sign & Security
 - **Sign**: Add digital signatures
@@ -87,6 +90,7 @@ All documentation available at [https://docs.stirlingpdf.com/](https://docs.stir
 - **OCR / Cleanup scans**: Optical Character Recognition
 - **Add Image**: Insert images into PDF
 - **Extract Images**: Extract embedded images
+- **Extract Attachments**: Retrieve embedded attachments
 - **Change Metadata**: Edit PDF metadata
 - **Get ALL Info on PDF**: Comprehensive PDF analysis
 - **Advanced Colour options**: Colour manipulation (various options for colour inversion, CMYK conversion)