Add an About dialog with build info (#2138)

add About dialog

src/frontend/qt_sdl/AboutDialog.cpp

@@ -0,0 +1,58 @@
+/*
+    Copyright 2016-2023 melonDS team
+
+    This file is part of melonDS.
+
+    melonDS is free software: you can redistribute it and/or modify it under
+    the terms of the GNU General Public License as published by the Free
+    Software Foundation, either version 3 of the License, or (at your option)
+    any later version.
+
+    melonDS is distributed in the hope that it will be useful, but WITHOUT ANY
+    WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+    FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License along
+    with melonDS. If not, see http://www.gnu.org/licenses/.
+*/
+
+#include "AboutDialog.h"
+
+#include <QDesktopServices>
+
+#include "ui_AboutDialog.h"
+
+#include "version.h"
+
+AboutDialog::AboutDialog(QWidget *parent) :
+    QDialog(parent), ui(new Ui::AboutDialog)
+{
+    ui->setupUi(this);
+
+    ui->lblVersionInfo->setText("Version " MELONDS_VERSION);
+#ifdef MELONDS_EMBED_BUILD_INFO
+    ui->lblBuildInfo->setText(
+        "Branch: " MELONDS_GIT_BRANCH "\n"
+        "Commit: " MELONDS_GIT_HASH "\n"
+        "Built by: " MELONDS_BUILD_PROVIDER
+    );
+#else
+    ui->lblBuildInfo->hide();
+#endif
+    adjustSize();
+}
+
+AboutDialog::~AboutDialog()
+{
+    delete ui;
+}
+
+void AboutDialog::openWebsite()
+{
+    QDesktopServices::openUrl(QUrl(MELONDS_URL));
+}
+
+void AboutDialog::openGitHub()
+{
+    QDesktopServices::openUrl(QUrl("https://github.com/melonDS-emu/melonDS"));;
+}