Qt: Allow rebinding keyboard controls (#779)

* Initial input UI draft

Co-Authored-By: Paris Oplopoios <parisoplop@gmail.com>

* More keybinding work

Co-Authored-By: Paris Oplopoios <parisoplop@gmail.com>

* Nit

Co-Authored-By: Paris Oplopoios <parisoplop@gmail.com>

* More nits

Co-Authored-By: Paris Oplopoios <parisoplop@gmail.com>

---------

Co-authored-by: Paris Oplopoios <parisoplop@gmail.com>

include/panda_qt/input_window.hpp

@@ -0,0 +1,32 @@
+#pragma once
+
+#include <QDialog>
+#include <QKeySequence>
+#include <QMap>
+#include <QPushButton>
+
+#include "input_mappings.hpp"
+
+class InputWindow : public QDialog {
+	Q_OBJECT
+
+  public:
+	InputWindow(QWidget* parent = nullptr);
+
+	void loadFromMappings(const InputMappings& mappings);
+	void applyToMappings(InputMappings& mappings) const;
+
+  signals:
+	void mappingsChanged();
+
+  protected:
+	bool eventFilter(QObject* obj, QEvent* event) override;
+
+  private:
+	QMap<QString, QPushButton*> buttonMap;
+	QMap<QString, QKeySequence> keyMappings;
+
+	QString waitingForAction;
+
+	void startKeyCapture(const QString& action);
+};