Copy code button

[Mylloon]

Closes #155.

• Update hljs to use the plugins
• The overlap problem was also present with the mathjax formulas, two birds with one stone
• Added an alias "c++" for cpp, it worked it the last version PineDocs used

Just, it's not rendering inline code like that

[xy2z]

Awesome! However, this doesn't seem to work for code files like style.css, there is no copy icon for those files. But it does work if the code is in a markdown file.

Reproduce: Make a new file called style.css, and add some css content:

 .class {
    padding: 4px;
}

Open the file in PineDocs and try to copy the code.

[Mylloon]

Should work now

[xy2z]

Thanks it works now.