Fix linking

Author: skotniczny

20_node.md

@@ -278,7 +278,7 @@ create such a file for each project, either manually or by running
 `npm init`. It contains some information about the project, such as
 its name and ((version)), and lists its dependencies.
 
-The robot simulation from [Chapter ?](#robot), as modularized in
+The robot simulation from [Chapter ?](robot), as modularized in
 [Exercise 10.1](modules#modular_robot), might have a `package.json`
 file like this:
 

src/render_latex.js

@@ -23,6 +23,7 @@ let chapters = fs.readdirSync(__dirname + "/..")
     .filter(file => /^\d{2}_\w+\.md$/.test(file))
     .sort()
     .map(file => /^\d{2}_(\w+)\.md$/.exec(file)[1])
+    .concat(['hints'])
 
 function escapeChar(ch) {
   switch (ch) {