feat: add "Add Page Labels" tool to the application

- Introduced a new tool for adding page labels to PDF documents, allowing users to apply Roman numerals, prefixes, and custom numbering ranges.
- Created a new HTML page for the tool with a user-friendly interface for file upload and label rule configuration.
- Implemented logic for handling file uploads, processing PDF files, and applying page labels based on user-defined rules.
- Added necessary types and utility functions for managing page label styles and normalization of start values.
- Updated main application configuration to include the new tool in the navigation.
- Added tests for page label utilities to ensure correct functionality.

src/js/main.ts

@@ -153,6 +153,7 @@ const init = async () => {
     'Edit Bookmarks': 'tools:editBookmarks',
     'Table of Contents': 'tools:tableOfContents',
     'Page Numbers': 'tools:pageNumbers',
+    'Add Page Labels': 'tools:addPageLabels',
     'Add Watermark': 'tools:addWatermark',
     'Header & Footer': 'tools:headerFooter',
     'Invert Colors': 'tools:invertColors',