Add About page for Khoj to Desktop app. Expose it via system tray

- Pass current khoj version from package.json to about page via
  electron IPC between backend js and frontend page
- Update Khoj information in default About screen as well, in case
  it's exposed anywhere else

src/interface/desktop/main.js

@@ -1,5 +1,6 @@
-const { app, BrowserWindow, ipcMain, Tray, Menu, nativeImage } = require('electron');
+const { app, BrowserWindow, ipcMain, Tray, Menu, nativeImage, shell } = require('electron');
 const todesktop = require("@todesktop/runtime");
+const khojPackage = require('./package.json');
 
 todesktop.init();
 
@@ -390,11 +391,12 @@ app.whenReady().then(() => {
 
     app.setAboutPanelOptions({
         applicationName: "Khoj",
-        applicationVersion: "0.0.1",
-        version: "0.0.1",
-        authors: "Khoj Team",
+        applicationVersion: khojPackage.version,
+        version: khojPackage.version,
+        authors: "Saba Imran, Debanjum Singh Solanky and contributors",
         website: "https://khoj.dev",
-        iconPath: path.join(__dirname, 'assets', 'khoj.png')
+        copyright: "GPL v3",
+        iconPath: path.join(__dirname, 'assets', 'icons', 'favicon-128x128.png')
     });
 
     app.on('ready', async() => {
@@ -418,6 +420,43 @@ app.on('window-all-closed', () => {
     if (process.platform !== 'darwin') app.quit()
 })
 
+/*
+** About Page
+*/
+
+let aboutWindow;
+
+function openAboutWindow() {
+    if (aboutWindow) { aboutWindow.focus(); return; }
+
+    aboutWindow = new BrowserWindow({
+        width: 400,
+        height: 400,
+        titleBarStyle: 'hidden',
+        show: false,
+        webPreferences: {
+            preload: path.join(__dirname, 'preload.js'),
+            nodeIntegration: true,
+        },
+    });
+
+    aboutWindow.loadFile('about.html');
+
+    // Pass OS, Khoj version to About page
+    aboutWindow.webContents.on('did-finish-load', () => {
+        aboutWindow.webContents.send('appInfo', { version: khojPackage.version, platform: process.platform });
+    });
+
+    // Open links in external browser
+    aboutWindow.webContents.setWindowOpenHandler(({ url }) => {
+        shell.openExternal(url);
+        return { action: 'deny' };
+    });
+
+    aboutWindow.once('ready-to-show', () => { aboutWindow.show(); });
+    aboutWindow.on('closed', () => { aboutWindow = null; });
+}
+
 /*
 **  System Tray Icon
 */
@@ -441,6 +480,7 @@ app.whenReady().then(() => {
         { label: 'Search', type: 'normal', click: () => { openWindow('search.html') }},
         { label: 'Configure', type: 'normal', click: () => { openWindow('config.html') }},
         { type: 'separator' },
+        { label: 'About Khoj', type: 'normal', click: () => { openAboutWindow(); } },
         { label: 'Quit', type: 'normal', click: () => { app.quit() } }
     ])