expand what files script/rlint will look at

* *.erb
 * *.rake
 * extensionless (i.e. scripts; rubocop itself will ensure they're ruby
   before actually inspecting them)

Change-Id: I86409e7b68b1ea5ff09c080a947dac6572bfae98
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/272222
Tested-by: Service Cloud Jenkins <svc.cloudjenkins@instructure.com>
QA-Review: Cody Cutrer <cody@instructure.com>
Product-Review: Cody Cutrer <cody@instructure.com>
Reviewed-by: Simon Williams <simon@instructure.com>

script/rlint

@@ -8,7 +8,7 @@ require 'optparse'
 
 linter_options = {
   linter_name: "Rubocop",
-  file_regex: /\.rb$/,
+  file_regex: %r{(?:\.e?rb|\.rake|\.gemspec|/[^./]+)$},
   format: "rubocop",
   command: "bin/rubocop",
   campsite_mode: false,