ensure fees decrease as target blocks increase, show priority on target blocks slider track

src/main/java/com/sparrowwallet/sparrow/net/FeeRatesSource.java

@@ -63,6 +63,7 @@ public enum FeeRatesSource {
         try(InputStream is = (proxy == null ? new URL(url).openStream() : new URL(url).openConnection(proxy).getInputStream()); Reader reader = new InputStreamReader(is, StandardCharsets.UTF_8)) {
             Gson gson = new Gson();
             ThreeTierRates threeTierRates = gson.fromJson(reader, ThreeTierRates.class);
+            Double lastRate = null;
             for(Integer blockTarget : defaultblockTargetFeeRates.keySet()) {
                 if(blockTarget < BLOCKS_IN_HALF_HOUR) {
                     blockTargetFeeRates.put(blockTarget, threeTierRates.fastestFee);
@@ -75,6 +76,11 @@ public enum FeeRatesSource {
                 } else {
                     blockTargetFeeRates.put(blockTarget, defaultblockTargetFeeRates.get(blockTarget));
                 }
+
+                if(lastRate != null) {
+                    blockTargetFeeRates.put(blockTarget, Math.min(lastRate, blockTargetFeeRates.get(blockTarget)));
+                }
+                lastRate = blockTargetFeeRates.get(blockTarget);
             }
 
             if(threeTierRates.minimumFee != null) {

src/main/resources/com/sparrowwallet/sparrow/wallet/send.css

@@ -104,3 +104,10 @@
 #transactionDiagram .utxo-label:hover .button .label .text {
     -fx-fill: -fx-text-base-color;
 }
+
+#targetBlocks .track {
+    -fx-background-color: -fx-shadow-highlight-color,
+        linear-gradient(to bottom, derive(-fx-text-box-border, -10%), -fx-text-box-border),
+        linear-gradient(to bottom, derive(-fx-control-inner-background, -9%), derive(-fx-control-inner-background, 0%), derive(-fx-control-inner-background, -5%), derive(-fx-control-inner-background, -12%)),
+        linear-gradient(to right, #c8416466 0%, #a0a1a766 50%, #a0a1a700 100%);
+}