Utils: add blockchair.com block explorer

src/settings.ui

@@ -175,6 +175,11 @@
            <string>moneroblocks.info</string>
           </property>
          </item>
+         <item>
+          <property name="text">
+           <string>blockchair.com</string>
+          </property>
+         </item>
         </widget>
        </item>
        <item row="4" column="0">

src/utils/utils.cpp

@@ -382,6 +382,11 @@ QString Utils::blockExplorerLink(const QString &blockExplorer, NetworkType::Type
             return QString("https://moneroblocks.info/tx/%1").arg(txid);
         }
     }
+    else if (blockExplorer == "blockchair.com") {
+        if (nettype == NetworkType::MAINNET) {
+            return QString("https://blockchair.com/monero/transaction/%1").arg(txid);
+        }
+    }
 
     switch (nettype) {
         case NetworkType::MAINNET: