style(style): update border styling of default button

src/assets/main.css

@@ -39,7 +39,7 @@ h3 {
 button {
     background-color: var(--color-button);
     color: var(--color-text);
-    border: none;
+    border-color: transparent;
     padding: 0.2rem 1rem;
     border-radius: 1rem;
     cursor: pointer;