Deprecate creole templates as they require modifying frozen string li…

…terals

It's a shame I didn't catch this earlier, due to warnings being silenced
for creole templates, but better late than never.  Creole's last commit
was 10 years ago, and it's last release was 12 years ago, so it appears
dead.

CHANGELOG.md

@@ -1,5 +1,6 @@
 ## master
 
+* Deprecate creole templates as they require modifying frozen string literals (jeremyevans)
 * Remove deprecated erubis, wikicloth, and maruku templates (jeremyevans)
 * Avoid spurious frozen string literal deprecation warning on Ruby 3.4.0-preview2+ (jeremyevans)
 

lib/tilt/creole.rb

@@ -2,6 +2,8 @@
 require_relative 'template'
 require 'creole'
 
+warn 'tilt/creole is deprecated, as creole requires modifying string literals', uplevel: 1
+
 allowed_opts = [:allowed_schemes, :extensions, :no_escape].freeze
 
 # Creole implementation. See: http://www.wikicreole.org/