ruby: add some qldoc for rack

Author: alexrford

ruby/ql/lib/codeql/ruby/frameworks/rack/internal/App.qll

@@ -14,6 +14,9 @@ private DataFlow::Node trackRackResponse(RP::PotentialResponseNode n) {
   trackRackResponse(TypeTracker::end(), n).flowsTo(result)
 }
 
+/**
+ * Provides modeling for Rack applications.
+ */
 module App {
   /**
    * A class that may be a rack application.

ruby/ql/lib/codeql/ruby/frameworks/rack/internal/Mime.qll

@@ -1287,6 +1287,9 @@ private predicate mimeTypeMatches(string ext, string mimeType) {
   ext = ".zmm" and mimeType = "application/vnd.handheld-entertainment+xml"
 }
 
+/**
+ * Provides modeling for the `Response` component of the `Rack` library.
+ */
 module Mime {
   class MimetypeCall extends DataFlow::CallNode {
     MimetypeCall() {

ruby/ql/lib/codeql/ruby/frameworks/rack/internal/Response.qll

@@ -6,6 +6,7 @@ private import codeql.ruby.DataFlow
 private import codeql.ruby.typetracking.TypeTracker
 private import App as A
 
+/** Contains implementation details for modelling `Rack::Response`. */
 module Private {
   private DataFlow::LocalSourceNode trackInt(TypeTracker t, int i) {
     t.start() and
@@ -33,6 +34,9 @@ module Private {
   }
 }
 
+/**
+ * Provides modeling for the `Response` component of the `Rack` library.
+ */
 module Public {
   bindingset[headerName]
   private DataFlow::Node getHeaderValue(ResponseNode resp, string headerName) {