This PR adds base64 to runtime dependency to suppress the following Ruby 3.3's warning:
$ ruby -wve 'require "http"'
ruby 3.3.0dev (2023-08-14T15:48:39Z master 52837fcec2) [x86_64-darwin22]
/Users/koic/.rbenv/versions/3.3.0-dev/lib/ruby/gems/3.3.0+0/gems/http-5.1.1/lib/http/chainable.rb:3:
warning: base64 which will be not part of the default gems since Ruby 3.4.0
This PR adds
base64
to runtime dependency to suppress the following Ruby 3.3's warning:cf: https://github.com/rails/rails/pull/48907