style(proxies): make "Test Latency" a fab like button

src/components/Proxies.js

@@ -39,7 +39,7 @@ export default function Proxies() {
     <div>
       <ContentHeader title="Proxies" />
       <div>
-        <div className={s0.btnGroup}>
+        <div className={s0.fabgrp}>
           <Button label="Test Latency" onClick={requestDelayAll} />
         </div>
         {groupNames.map(groupName => {

src/components/Proxies.module.scss

@@ -5,9 +5,8 @@
   padding: 10px 40px;
 }
 
-.btnGroup {
-  color: #eee;
-  padding: 0 40px;
-  display: flex;
-  justify-content: flex-end;
+.fabgrp {
+  position: fixed;
+  right: 20px;
+  bottom: 20px;
 }

src/components/ProxyGroup.module.scss

@@ -1,5 +1,7 @@
 .header {
-  h2 {
+  > h2 {
+    margin-top: 0;
+
     span:nth-child(2) {
       font-size: 12px;
       color: #777;