Copy to clipboard feature for code block (#152)

Co-authored-by: Jacky Zhao <j.zhao2k19@gmail.com>

data/config.yaml

@@ -4,6 +4,7 @@ openToc: false
 enableLinkPreview: true
 enableLatex: true
 enableCodeBlockTitle: true
+enableCodeBlockCopy: true
 enableSPA: true
 enableFooter: true
 enableContextualBacklinks: true