Update look and feel of examples and copy buttons

[mdo]

Restores some of the look and feel from previous versions :). More specifically:

• Adds border around the code snippets
• Removes the blue coloring around Copy buttons
• Adds the language at the top of each code snippet
• Includes some messy code for attaching multiple code snippets to an example (see above screenshot)—would love help cleaning this up somehow. Maybe I just wrap it all in some custom HTML? Something else?

/cc @XhmikosR

[mdo]

Going to ship this as-is and iterate in other PRs as we go :).

[XhmikosR]

@mdo we need to get this fixed :)

bootstrap/site/assets/scss/_syntax.scss

Lines 87 to 102 in cdf56e0

	.chroma {
	.language-bash,
	.language-sh {
	&::before {
	color: #009;
	content: "$ ";
	user-select: none;
	}
	}
	.language-powershell::before {
	color: #009;
	content: "PM> ";
	user-select: none;
	}
	}