UI: Add pause support

Adds support for pausing recordings.  When settings are eligible for
recordings, a pause button will appear next to the recording button.  If
the settings are not eligible, it will warn the user in the output
settings that they cannot pause recordings if those settings are used.

UI/record-button.hpp

@@ -0,0 +1,12 @@
+#pragma once
+
+#include <QPushButton>
+
+class RecordButton : public QPushButton {
+	Q_OBJECT
+
+public:
+	inline RecordButton(QWidget *parent = nullptr) : QPushButton(parent) {}
+
+	virtual void resizeEvent(QResizeEvent *event) override;
+};