qml: Introduce minus icon

Author: jarolrod

src/qml/bitcoin_qml.qrc

@@ -77,6 +77,7 @@
         <file alias="export">res/icons/export.png</file>
         <file alias="gear">res/icons/gear.png</file>
         <file alias="info">res/icons/info.png</file>
+        <file alias="minus">res/icons/minus.png</file>
         <file alias="network-dark">res/icons/network-dark.png</file>
         <file alias="network-light">res/icons/network-light.png</file>
         <file alias="shutdown">res/icons/shutdown.png</file>

src/qml/imageprovider.cpp

@@ -97,6 +97,11 @@ QPixmap ImageProvider::requestPixmap(const QString& id, QSize* size, const QSize
         return QIcon(":/icons/info").pixmap(requested_size);
     }
 
+    if (id == "minus") {
+        *size = requested_size;
+        return QIcon(":/icons/minus").pixmap(requested_size);
+    }
+
     if (id == "network-dark") {
         *size = requested_size;
         return QIcon(":/icons/network-dark").pixmap(requested_size);