Added a deprecation notice to the gem description

Author: sgravrock

jasmine.gemspec

@@ -11,7 +11,17 @@ Gem::Specification.new do |s|
 
   s.authors            = ["Gregg Van Hove"]
   s.summary            = %q{JavaScript BDD framework}
-  s.description        = %q{Test your JavaScript without any framework dependencies, in any environment, and with a nice descriptive syntax.}
+  s.description        = <<~DESC
+    Test your JavaScript without any framework dependencies, in any environment,
+    and with a nice descriptive syntax.
+
+    Jasmine for Ruby is deprecated. We recommend using the
+    jasmine-browser-runner NPM package instead. It supports all the same
+    scenarios as this gem plus Webpacker. See
+    <https://jasmine.github.io/setup/browser.html> for setup instructions, and
+    <https://github.com/jasmine/jasmine-gem/blob/main/release_notes/3.9.0.md>
+    for other options.
+  DESC
   s.email              = %q{jasmine-js@googlegroups.com}
   s.homepage           = "http://jasmine.github.io/"
   s.license            = "MIT"