Syntax highlighting (#691)

* Syntax highlighting mostly... Exists.

* Add dependency to dockerfile

* Handle non-existent languages better

* Make the default a bit nicer

* Improve highlighting. Clean up function

* Add dark theme, add the comment scope to the allowed classes

* update build env

* Address review comments

* Use find_syntax_by_token which produces the desired behavior

* Change flat_map into flatten
(commit cargo.lock)

assets/themes/default/_dark_variables.scss

@@ -17,3 +17,12 @@ $text-color: $white;
 $primary: $purple;
 $primary-text-color: $white; // text color on primary background (buttons for instance)
 $success-color: $blue;
+
+//Code Highlighting
+
+$code-keyword-color: #f79ac1;
+$code-source-color: #a6f0ab;
+$code-constant-color: #dfec84;
+$code-operator-color: #eddf95;
+$code-string-color: #f2ae60;
+$code-comment-color: #a3b4f9;

assets/themes/default/_global.scss

@@ -623,3 +623,28 @@ figure {
     }
   }
 }
+
+//highlighting
+code {
+  .constant{
+      color: $code-constant-color;
+  }
+  .string{
+      color: $code-string-color;
+  }
+  .keyword.type,.keyword.control,.type{
+      color: $code-keyword-color;
+  }
+  .keyword.operator{
+      color: $code-operator-color;
+  }
+  .source{
+      color: $code-source-color;
+  }
+  .comment{
+      color: $code-comment-color;
+  }
+  .function{
+      color:inherit;
+  }
+}

assets/themes/default/_variables.scss

@@ -27,3 +27,11 @@ $margin: 0 $horizontal-margin;
 $route159: "Route159", serif;
 $playfair: "Playfair Display", serif;
 $lora: "Lora", serif;
+
+//Code Highlighting
+$code-keyword-color: #45244a;
+$code-source-color: #4c588c;
+$code-constant-color: scale-color(magenta,$lightness:-5%);
+$code-operator-color: scale-color($code-source-color,$lightness:-5%);
+$code-string-color: #8a571c;
+$code-comment-color: #1c4c8a;