fix: ensure gap between SearchField input and button is transparent (#4006)

Author: brian-smith-tcril

src/SearchField/index.scss

@@ -91,6 +91,10 @@
   &.pgn__searchfield--external {
     border: none;
 
+    .pgn__searchfield-form {
+      background-color: transparent;
+    }
+
     &.has-focus {
       box-shadow: none;
 
@@ -112,6 +116,7 @@
     display: flex;
     align-items: center;
     width: 100%;
+    background-color: var(--pgn-color-search-field-form-bg);
     border: var(--pgn-size-search-field-border-width-base) solid var(--pgn-color-search-field-border-base);
 
     &:hover,