feat: add initial project setup with core PDF tools and utilities

- Implement core PDF manipulation tools (split, merge, convert, etc.)
- Add state management and UI utilities
- Set up build configuration with Vite and TailwindCSS
- Include essential dependencies for PDF processing
- Add gitignore and basic project configuration files

src/js/logic/split-in-half.ts

@@ -0,0 +1,53 @@
+import { showLoader, hideLoader, showAlert } from '../ui.js';
+import { downloadFile } from '../utils/helpers.js';
+import { state } from '../state.js';
+
+import { PDFDocument as PDFLibDocument, rgb } from 'pdf-lib';
+
+export async function splitInHalf() {
+    // @ts-expect-error TS(2339) FIXME: Property 'value' does not exist on type 'HTMLEleme... Remove this comment to see the full error message
+    const splitType = document.getElementById('split-type').value;
+    if (!state.pdfDoc) {
+        showAlert('Error', 'No PDF document is loaded.');
+        return;
+    }
+    showLoader('Splitting PDF pages...');
+    try {
+        const newPdfDoc = await PDFLibDocument.create();
+        const pages = state.pdfDoc.getPages();
+
+        for (let i = 0; i < pages.length; i++) {
+            const originalPage = pages[i];
+            const { width, height } = originalPage.getSize();
+            const whiteColor = rgb(1, 1, 1); // For masking
+
+            showLoader(`Processing page ${i + 1} of ${pages.length}...`);
+
+            // Copy the page twice for all split types
+            const [page1] = await newPdfDoc.copyPages(state.pdfDoc, [i]);
+            const [page2] = await newPdfDoc.copyPages(state.pdfDoc, [i]);
+
+            switch (splitType) {
+                case 'vertical':
+                    page1.setCropBox(0, 0, width / 2, height);
+                    page2.setCropBox(width / 2, 0, width / 2, height);
+                    break;
+                case 'horizontal':
+                    page1.setCropBox(0, height / 2, width, height / 2); // Top half
+                    page2.setCropBox(0, 0, width, height / 2);        // Bottom half
+                    break;
+            }
+            newPdfDoc.addPage(page1);
+            newPdfDoc.addPage(page2);
+        }
+
+        const newPdfBytes = await newPdfDoc.save();
+        downloadFile(new Blob([newPdfBytes], { type: 'application/pdf' }), 'split-half.pdf');
+
+    } catch (e) {
+        console.error(e);
+        showAlert('Error', 'An error occurred while splitting the PDF.');
+    } finally {
+        hideLoader();
+    }
+}