Add Ruby 3.4 support

Ruby 3.4 is removing the `base64` default gem to [became bundled](https://rubyreferences.github.io/rubychanges/3.4.html#default-gems-that-became-bundled)

Making the current webmock (v3.16.2) gem incompatible because it has a dependency on the `base64` gem,
to fix it we are bumping webmock to v3.20.0 which [removed the
`base64`](bblimke/webmock#1046) dependency.

As an alternative solution, we can leave the current `webmock` version untoched
and add the `base64` gem as a dependency.

Given this message: `limited on purpose, new versions don't work with old rubies`
we might lost support of some old rubies.

Author: JuanVqz

.github/workflows/main.yml

@@ -13,7 +13,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        ruby-version: ["3.3", "3.2", "3.1", "3.0", "2.7", "2.6"]
+        ruby-version: ["3.4", "3.3", "3.2", "3.1", "3.0", "2.7", "2.6"]
 
     steps:
       - uses: actions/checkout@v2

next_rails.gemspec

@@ -13,7 +13,7 @@ Gem::Specification.new do |spec|
   spec.homepage     = "https://github.com/fastruby/next_rails"
   spec.license       = "MIT"
 
-  spec.required_ruby_version = ">= 2.0"
+  spec.required_ruby_version = ">= 2.0", "< 3.5"
 
   spec.files         = `git ls-files -z`.split("\x0").reject do |f|
     f.match(%r{^(test|spec|features)/})
@@ -30,5 +30,5 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency "timecop", "~> 0.9.1"
   spec.add_development_dependency "byebug"
   spec.add_development_dependency "rexml", "3.3.8" # limited on purpose, new versions don't work with old rubies
-  spec.add_development_dependency "webmock", "3.16.2" # limited on purpose, new versions don't work with old rubies
+  spec.add_development_dependency "webmock", "3.20.0"
 end