feat: add autocompletion for commands

partially copied code from emojimodel.h

src/commandmodel.h

@@ -0,0 +1,58 @@
+// SPDX-FileCopyrightText: 2021 Srevin Saju <srevinsaju@sugarlabs.org>
+// SPDX-License-Identifier: GPL-3.0-only
+
+#pragma once
+
+#include <QObject>
+#include <QSettings>
+#include <QVariant>
+#include <QVector>
+#include <utility>
+
+struct Command {
+    Command(QString u, QString s)
+        : command(std::move(std::move(u)))
+        , help(std::move(std::move(s)))
+    {
+    }
+    Command() = default;
+
+    friend QDataStream &operator<<(QDataStream &arch, const Command &object)
+    {
+        arch << object.command;
+        arch << object.help;
+        return arch;
+    }
+
+    friend QDataStream &operator>>(QDataStream &arch, Command &object)
+    {
+        arch >> object.command;
+        arch >> object.help;
+        return arch;
+    }
+
+    QString command;
+    QString help;
+
+Q_GADGET
+    Q_PROPERTY(QString command MEMBER command)
+    Q_PROPERTY(QString help MEMBER help)
+};
+
+Q_DECLARE_METATYPE(Command)
+
+class CommandModel : public QObject
+{
+Q_OBJECT
+
+public:
+    explicit CommandModel(QObject *parent = nullptr)
+        : QObject(parent)
+    {
+    }
+
+    Q_INVOKABLE static QVariantList filterModel(const QString &filter);
+
+private:
+    static const QVariantList matrix;
+};