Fix for copy-btn in gist (#342)

extension/content.css

@@ -534,6 +534,6 @@ td.blob-code.blob-code-deletion:before {
 }
 
 /* copy button for gists margin */
-.copy-btn {
+.gist-copy-btn {
 	margin: 0 10px 0 0;
 }

extension/copy-gist.js

@@ -14,7 +14,7 @@ window.addGistCopyButton = () => {
 		const isSourceCodeClass = commonContainer.children[1].classList.contains('blob-wrapper');
 		const gistUri = $gistsSibling[i].href;
 		if (isSourceCodeClass) {
-			$(`<a href="${gistUri}" class="btn btn-sm copy-btn">Copy</a>`).insertBefore($gistsSibling[i]);
+			$(`<a href="${gistUri}" class="btn btn-sm copy-btn gist-copy-btn">Copy</a>`).insertBefore($gistsSibling[i]);
 		}
 	}