Add base64 gem to rails 7.0 and 7.1

```
> BUNDLE_GEMFILE=/home/runner/work/loga/loga/gemfiles/rails70.gemfile bundle exec rspec
/home/runner/.rubies/ruby-head/lib/ruby/gems/3.4.0+0/gems/activesupport-7.0.8/lib/active_support/message_verifier.rb:4: warning: base64 was loaded from the standard library, but is not part of the default gems since Ruby 3.4.0. Add base64 to your Gemfile or gemspec.

Failure/Error: require 'rails'

LoadError:
  cannot load such file -- base64
```

This one.. most probably won't work but let's try.

https://stdgems.org/base64/

The root issue is that in old ruby version base64 0.1.1 should be used
and base64 0.2.0 is just for ruby 3.3.0

If 0.2.0 is installed on ruby 3.2, it will just crash..

Appraisals

@@ -61,10 +61,12 @@ end
 if Gem::Version.new(RUBY_VERSION) > Gem::Version.new('3.0.0')
   appraise 'rails70' do
     gem 'rails', '~> 7.0.0'
+    gem 'base64'
   end
 
   appraise 'rails71' do
     gem 'rails', '~> 7.1.0'
+    gem 'base64'
   end
 end
 

gemfiles/rails70.gemfile

@@ -3,6 +3,7 @@
 source "https://rubygems.org"
 
 gem "rails", "~> 7.0.0"
+gem "base64"
 
 group :development do
   gem "appraisal"

gemfiles/rails71.gemfile

@@ -3,6 +3,7 @@
 source "https://rubygems.org"
 
 gem "rails", "~> 7.1.0"
+gem "base64"
 
 group :development do
   gem "appraisal"