fix: use proper selector for api-demo copy button styles (#201)

Author: web-padawan

.changeset/warm-mails-fry.md

@@ -0,0 +1,9 @@
+---
+"@api-viewer/demo": patch
+"@api-viewer/common": patch
+"@api-viewer/docs": patch
+"@api-viewer/tabs": patch
+"api-viewer-element": patch
+---
+
+Use proper selector for demo copy button styles

packages/api-demo/src/styles.ts

@@ -60,7 +60,7 @@ const highlightTheme = css`
 `;
 
 const demoStyles = css`
-  button {
+  [part='button'] {
     position: absolute;
     top: 0.5rem;
     right: 0.5rem;
@@ -72,8 +72,8 @@ const demoStyles = css`
     color: var(--ave-button-color, #fff);
   }
 
-  button:focus,
-  button:hover {
+  [part='button']:focus,
+  [part='button']:hover {
     background: var(--ave-button-active-background, rgba(0, 0, 0, 0.6));
   }