Document banned npm names (#381)

* Document banned npm names

Cherry-picked from microsoft/dtslint@1ed6a62

Resolves microsoft/dtslint#351 (comment) by @sandersn

* Update link to PR

Author: LinqLover

packages/dtslint/src/index.ts

@@ -249,6 +249,15 @@ function assertPathIsInDefinitelyTyped(dirPath: string): void {
   }
 }
 
+/**
+ * Starting at some point in time, npm has banned all new packages whose names
+ * contain the word `download`. However, some older packages exist that still
+ * contain this name.
+ * @NOTE for contributors: The list of literal exceptions below should ONLY be
+ * extended with packages for which there already exists a corresponding type
+ * definition package in the `@types` scope. More information:
+ * https://github.com/microsoft/DefinitelyTyped-tools/pull/381.
+ */
 function assertPathIsNotBanned(dirPath: string) {
   const basedir = basename(dirPath);
   if (