📝 Improved documentation

.rubocop_gradual.lock

@@ -1,6 +1,6 @@
 {
-  "README.md:25157257": [
-    [502, 6, 1, "Lint/Syntax: unexpected token tCOMMA\n(Using Ruby 2.3 parser; configure using `TargetRubyVersion` parameter, under `AllCops`)", 177545]
+  "README.md:2858832830": [
+    [504, 6, 1, "Lint/Syntax: unexpected token tCOMMA\n(Using Ruby 2.3 parser; configure using `TargetRubyVersion` parameter, under `AllCops`)", 177545]
   ],
   "Rakefile:687725157": [
     [8, 3, 30, "Style/MethodCallWithArgsParentheses: Use parentheses for method calls with arguments.", 2786900295],

README.md

@@ -63,13 +63,15 @@ then this is the gem for you.
 
 ## Compatibility
 
-⚙️ Compatible with all versions of Ruby >= 2.3.
+⚙️ Compatible with all versions of Ruby >= 2.3, plus JRuby and Truffleruby.
 ⚙️ Compatible with all Ruby web Frameworks (Hanami, Roda, Sinatra, Rails).
 ⚙️ Compatible with all versions of Rails from 3.0 - 7.1+.
 ⚙️ Compatible with scripted usage of Mail gem outside a web framework.
 ⚙️ Compatible with [`sendgrid-actionmailer`](https://github.com/eddiezane/sendgrid-actionmailer)'s support for personalizations, and will override email addresses there according to the configuration.
 ⚙️ If this gem is not compatible with your use case, and you'd like it to be, I'd like to hear about it!
 
+It was a slog getting (very nearly) the entire compatibility matrix working with Github Actions, [`appraisal`](https://github.com/thoughtbot/appraisal), and [`combustion`](https://github.com/pat/combustion), and I'm very interested in hearing about ways to improve it!
+
 ## 🛞 DVCS
 
 This project does not trust any one version control system,