Enable 'debug: true' option on asset tag helpers

[rlue]

From Section 3.3 of the Edge Guides on the Asset Pipeline:

Debug mode can also be enabled in Rails helper methods:

<%= stylesheet_link_tag "application", debug: true %>
<%= javascript_include_tag "application", debug: true %>

The :debug option is redundant if debug mode is already on.

But per lines 140 and 169 of Sprockets::Rails::Helper:

if options["debug"] != false && request_debug_assets?

This conditional allows debugging to be explicitly disabled on a tag when Rails.application.config.assets.debug == true, but not vice versa.

This PR uses the naive solution (simply adding || options["debug"]) rather than performing more extensive refactoring, since comments indicate that this method is slated for deprecation anyway.

[rails-bot]

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