Fine-tune appearance of buttons in calling interface UI

GitLab: #97

Change-Id: Iecf16921171196547e2a392ba6826971ca23ac47
diff --git a/client/src/components/SvgIcon.tsx b/client/src/components/SvgIcon.tsx
index 0b8b9ed..88423b1 100644
--- a/client/src/components/SvgIcon.tsx
+++ b/client/src/components/SvgIcon.tsx
@@ -799,3 +799,15 @@
     </SvgIcon>
   );
 };
+
+export const WindowIcon = (props: SvgIconProps) => {
+  return (
+    <SvgIcon {...props} viewBox="0 0 24 24">
+      <path
+        d="M20.5,0.8h-17C2,0.8,0.8,2,0.8,3.5v17c0,1.5,1.2,2.7,2.7,2.7h17c1.5,0,2.7-1.2,2.7-2.7v-17C23.2,2,22,0.8,20.5,0.8z
+    M3.5,2.2h17c0.7,0,1.3,0.6,1.3,1.3v0.1H2.2V3.5C2.2,2.8,2.8,2.2,3.5,2.2z M7.7,21.8H3.5c-0.7,0-1.3-0.6-1.3-1.3V5h5.5h1.4h12.7
+   v15.5c0,0.7-0.6,1.3-1.3,1.3H9.1H7.7z"
+      />
+    </SvgIcon>
+  );
+};