feat: add autocompletion for commands

partially copied code from emojimodel.h

src/commandmodel.cpp

@@ -0,0 +1,32 @@
+// SPDX-FileCopyrightText: 2021 Srevin Saju <srevinsaju@sugarlabs.org>
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#include <QDebug>
+
+#include "commandmodel.h"
+
+
+QVariantList CommandModel::filterModel(const QString &filter)
+{
+    QVariantList result;
+
+    for (const QVariant &e : matrix) {
+        auto command = qvariant_cast<Command>(e);
+        if (command.command.startsWith(filter)) {
+            result.append(e);
+            if (result.length() > 10) {
+                return result;
+            }
+        }
+    }
+
+    return result;
+}
+
+
+// the help messages are taken from Element (web matrix client, app.element.io)
+const QVariantList CommandModel::matrix = {
+    QVariant::fromValue(Command{"/join", "Join a given room with address"}),
+    QVariant::fromValue(Command{"/me", "Displays action"}),
+
+};