style: Fix close button styling

src/main/webapp/css/mapModal.css

@@ -43,6 +43,22 @@
     font-size: 0.9rem; /* Make font-size of popup larger */
 }
 
+.close-button {
+    position: absolute;
+    top: 10px;
+    right: 15px;
+    font-size: 40px;
+    color: white;
+    background-color: transparent;
+    border: none;
+    cursor: pointer;
+    z-index: 1500;
+}
+
+.close-button:hover {
+    color: #ddd;
+}
+
 #pointForm {
     z-index: 1200;
     position: absolute;