fix(accessibility): don't use white on yellow text

White on yellow presents accessibility challenges and should be avoided.
Change the white on yellow used in highlighted buttons for a darker
colour against the yellow background.

Fix #356

app/components/Contacts/ConnectManually.scss

@@ -124,6 +124,8 @@
 
     &.active {
       background: $gold;
+      color: $spaceblue;
+      font-weight: bold;
       opacity: 1;
 
       &:hover {

app/components/Contacts/SubmitChannelForm.scss

@@ -132,6 +132,8 @@
 
     &.active {
       background: $gold;
+      color: $spacegrey;
+      font-weight: bold;
       opacity: 1;
 
       &:hover {

app/components/Form/Pay.scss

@@ -163,6 +163,8 @@
 
       &.active {
         background: $gold;
+        color: $spaceblue;
+        font-weight: bold;
         opacity: 1;
 
         &:hover {

app/components/Form/Request.scss

@@ -142,6 +142,8 @@
 
       &.active {
         background: $gold;
+        color: $spaceblue;
+        font-weight: bold;
         opacity: 1;
 
         &:hover {