Improve highlight styles support

Closes #6

README.md

@@ -114,8 +114,8 @@ to add a style to code blocks.
 
 The `--highlight-style` option can receive the name of a
 [Hightlight.js style](https://github.com/highlightjs/highlight.js/tree/master/src/styles)
-(file name without extension, e.g. `solarized-dark`) or the path to a custom
-style file (a local path or a HTTP URL).
+(file name without extension, e.g. `monokai`) or the path to a custom style
+file (a local path or a HTTP URL).
 
 #### Additional features
 

src/style.js

@@ -155,7 +155,7 @@ export class Style {
   async loadHighlightStyle(style) {
     // Predefined highlight style
     let stylePath = paths.join(HLJS_STYLES_PATH, style + ".css");
-    if (!/^[\w-]+$/.test(style) || !(await files.isReadable(stylePath))) {
+    if (!/^(\w+\/)?[\w-]+$/.test(style) || !(await files.isReadable(stylePath))) {
       // Custom highlight style
       stylePath = await this.validate(style, style, "highlight style");
     }

test/processor.test.js

@@ -138,6 +138,22 @@ describe("Processor", () => {
     });
   });
 
+  describe('mdtodoc doc.md -l "page" -t "github" --highlight-style "base16/solarized-dark"', () => {
+    it("should use a highlight style from the base16 folder", async () => {
+      const proc = new Processor({
+        layout: "page",
+        theme: "github",
+        highlightStyle: "base16/solarized-dark",
+      });
+      const src = buildDataPath("README.md");
+      const dst = buildDataPath("README.html");
+      await proc.process([src]);
+      assert.isTrue(await files.exists(dst));
+      const html = await files.readAllText(dst);
+      assert.include(html, "background:#002b36");
+    });
+  });
+
   describe('mdtodoc doc.md -l "page" -t "github" -s "atom-one-light" --numbered-headings --code-copy --mermaid', () => {
     it("should enable additional extensions", async () => {
       const proc = new Processor({