feat: show open source licenses in About screen

Implement the dormant Library Licenses entry in the About Us screen
using Flutter's built-in showLicensePage, which lists the licenses of
all bundled open-source libraries. Relabel the existing license row to
App License (Apache 2.0) and localize the new strings (en/hi/it).

Author: bhavjsh

lib/l10n/app_en.arb

@@ -60,6 +60,9 @@
   "contactUs": "Contact Us",
   "contactWithUs": "Contact With Us",
   "license": "License",
+  "appLicense": "App License (Apache 2.0)",
+  "openSourceLicenses": "Open Source Licenses",
+  "openSourceLicensesDescription": "View licenses of the open source libraries used in this app.",
   "speed": "Speed",
   "speedTitle": "Speed",
   "animation": "Animation",

lib/l10n/app_hi.arb

@@ -52,6 +52,9 @@
     "fossasiaContributors": "FOSSASIA टीम द्वारा",
     "contactWithUs": "हमसे संपर्क करें",
     "license": "लाइसेंस",
+    "appLicense": "ऐप लाइसेंस (Apache 2.0)",
+    "openSourceLicenses": "ओपन सोर्स लाइसेंस",
+    "openSourceLicensesDescription": "इस ऐप में उपयोग की गई ओपन सोर्स लाइब्रेरी के लाइसेंस देखें।",
     "speed": "स्पीड",
     "speedTitle": "स्पीड",
     "animation": "एनिमेशन",

lib/l10n/app_it.arb

@@ -60,6 +60,9 @@
   "contactUs": "Contattaci",
   "contactWithUs": "Contatta con Noi",
   "license": "Licenza",
+  "appLicense": "Licenza dell'app (Apache 2.0)",
+  "openSourceLicenses": "Licenze open source",
+  "openSourceLicensesDescription": "Visualizza le licenze delle librerie open source utilizzate in questa app.",
   "speed": "Velocità",
   "speedTitle": "Velocità",
   "animation": "Animazione",

lib/view/about_us_screen.dart

@@ -204,7 +204,7 @@ class _AboutUsScreenState extends State<AboutUsScreen> {
                         fit: BoxFit.contain,
                       ),
                       title: Text(
-                        l10n.license,
+                        l10n.appLicense,
                         style: GoogleFonts.sora(
                           fontSize: 16,
                           fontWeight: FontWeight.w500,
@@ -223,24 +223,42 @@ class _AboutUsScreenState extends State<AboutUsScreen> {
                       onTap: () => openUrl(
                           'https://github.com/fossasia/badgemagic-app/blob/development/LICENSE'),
                     ),
-                    // ListTile(
-                    //   leading: Image.asset('assets/icons/book.png', height: 40),
-                    //   title: Text(
-                    //     'Library Licenses',
-                    //     style: GoogleFonts.sora(
-                    //         fontSize: 16,
-                    //         fontWeight: FontWeight.w500,
-                    //         color: Colors.black),
-                    //   ),
-                    //   subtitle: Text(
-                    //     'Check third-party libs used on Badge Magic.',
-                    //     style: GoogleFonts.sora(
-                    //         fontSize: 12,
-                    //         fontWeight: FontWeight.w500,
-                    //         color: Colors.grey),
-                    //   ),
-                    //   onTap: () => showLicenseDialog(context),
-                    // ),
+                    ListTile(
+                      leading: const Icon(
+                        Icons.description_outlined,
+                        size: 38,
+                        color: Colors.black,
+                      ),
+                      title: Text(
+                        l10n.openSourceLicenses,
+                        style: GoogleFonts.sora(
+                          fontSize: 16,
+                          fontWeight: FontWeight.w500,
+                          color: Colors.black,
+                        ),
+                      ),
+                      subtitle: Text(
+                        l10n.openSourceLicensesDescription,
+                        style: GoogleFonts.sora(
+                          fontSize: 12,
+                          fontWeight: FontWeight.w500,
+                          color: Colors.grey,
+                        ),
+                        softWrap: true,
+                      ),
+                      onTap: () => showLicensePage(
+                        context: context,
+                        applicationName: l10n.appTitle,
+                        applicationIcon: Padding(
+                          padding: const EdgeInsets.all(8.0),
+                          child: Image.asset(
+                            'assets/icons/icon.png',
+                            height: 48,
+                            fit: BoxFit.contain,
+                          ),
+                        ),
+                      ),
+                    ),
                   ],
                 ),
               ),