Provide Bash/Shell code syntax in Rich Text Editor

Closes #322

gui/public/prism/prism.css

@@ -1,5 +1,5 @@
-/* PrismJS 1.15.0
-https://prismjs.com/download.html?#themes=prism-solarizedlight&languages=markup+css+clike+javascript+c+csharp+cpp+coffeescript+ruby+docker+elixir+markup-templating+erlang+fsharp+git+go+less+handlebars+haskell+http+java+json+markdown+makefile+nginx+objectivec+perl+php+sql+powershell+scss+python+jsx+typescript+rust+swift+yaml&plugins=line-numbers */
+/* PrismJS 1.17.1
+https://prismjs.com/download.html#themes=prism-solarizedlight&languages=markup+css+clike+javascript+c+csharp+bash+cpp+aspnet+coffeescript+clojure+ruby+markup-templating+docker+elixir+erlang+fsharp+git+go+graphql+less+handlebars+haskell+http+java+php+markdown+json+latex+makefile+typescript+nginx+objectivec+perl+sql+powershell+scss+python+jsx+rust+plsql+swift+yaml+toml+regex+wasm&plugins=line-numbers+toolbar+highlight-keywords+show-language */
 /*
  Solarized Color Schemes originally by Ethan Schoonover
  http://ethanschoonover.com/solarized
@@ -34,6 +34,7 @@ code[class*="language-"],
 pre[class*="language-"] {
 	color: #657b83; /* base00 */
 	font-family: Consolas, Monaco, 'Andale Mono', 'Ubuntu Mono', monospace;
+	font-size: 1em;
 	text-align: left;
 	white-space: pre;
 	word-spacing: normal;
@@ -192,3 +193,68 @@ pre[class*="language-"].line-numbers > code {
 			text-align: right;
 		}
 
+div.code-toolbar {
+	position: relative;
+}
+
+div.code-toolbar > .toolbar {
+	position: absolute;
+	top: .3em;
+	right: .2em;
+	transition: opacity 0.3s ease-in-out;
+	opacity: 0;
+}
+
+div.code-toolbar:hover > .toolbar {
+	opacity: 1;
+}
+
+/* Separate line b/c rules are thrown out if selector is invalid.
+   IE11 and old Edge versions don't support :focus-within. */
+div.code-toolbar:focus-within > .toolbar {
+	opacity: 1;
+}
+
+div.code-toolbar > .toolbar .toolbar-item {
+	display: inline-block;
+}
+
+div.code-toolbar > .toolbar a {
+	cursor: pointer;
+}
+
+div.code-toolbar > .toolbar button {
+	background: none;
+	border: 0;
+	color: inherit;
+	font: inherit;
+	line-height: normal;
+	overflow: visible;
+	padding: 0;
+	-webkit-user-select: none; /* for button */
+	-moz-user-select: none;
+	-ms-user-select: none;
+}
+
+div.code-toolbar > .toolbar a,
+div.code-toolbar > .toolbar button,
+div.code-toolbar > .toolbar span {
+	color: #bbb;
+	font-size: .8em;
+	padding: 0 .5em;
+	background: #f5f2f0;
+	background: rgba(224, 224, 224, 0.2);
+	box-shadow: 0 2px 0 0 rgba(0,0,0,0.2);
+	border-radius: .5em;
+}
+
+div.code-toolbar > .toolbar a:hover,
+div.code-toolbar > .toolbar a:focus,
+div.code-toolbar > .toolbar button:hover,
+div.code-toolbar > .toolbar button:focus,
+div.code-toolbar > .toolbar span:hover,
+div.code-toolbar > .toolbar span:focus {
+	color: inherit;
+	text-decoration: none;
+}
+