utils: perform portable path sanitisation of URLs

Some file systems have restrictions on character sets which are valid
file name characters.  Add a filter for the Windows file system
character set restrictions.  We replace them with `_` to match the
behaviour in the DocC bundle generation after apple/swift-docc#668.

src/utils/data.js

@@ -56,7 +56,7 @@ export async function fetchData(path, params = {}, options = {}) {
 }
 
 function createDataPath(path) {
-  const dataPath = path.replace(/\/$/, '');
+  const dataPath = path.replace(/\/$/, "").replace(/[<>:"\/\\|*]/, "_");
   return `${normalizePath(['/data', dataPath])}.json`;
 }