Move development dependencies to Gemfile

see rubygems/rubygems#1104 for context

Gemfile

@@ -1,4 +1,13 @@
+# frozen_string_literal: true
+
 source 'https://rubygems.org'
 
 # Specify your gem's dependencies in themoviedb.gemspec
-gemspec
+gemspec
+
+gem 'minitest', '~> 5.16'
+gem 'rake', '~> 13.0'
+gem 'rspec'
+gem 'rubocop', '~> 1.21'
+gem 'vcr'
+gem 'webmock'

Gemfile.lock

@@ -0,0 +1,89 @@
+PATH
+  remote: .
+  specs:
+    themoviedb (1.0.1)
+      httparty
+
+GEM
+  remote: https://rubygems.org/
+  specs:
+    addressable (2.8.7)
+      public_suffix (>= 2.0.2, < 7.0)
+    ast (2.4.2)
+    base64 (0.2.0)
+    bigdecimal (3.1.8)
+    crack (1.0.0)
+      bigdecimal
+      rexml
+    csv (3.3.0)
+    diff-lcs (1.5.1)
+    hashdiff (1.1.1)
+    httparty (0.22.0)
+      csv
+      mini_mime (>= 1.0.0)
+      multi_xml (>= 0.5.2)
+    json (2.7.2)
+    language_server-protocol (3.17.0.3)
+    mini_mime (1.1.5)
+    minitest (5.25.1)
+    multi_xml (0.7.1)
+      bigdecimal (~> 3.1)
+    parallel (1.26.3)
+    parser (3.3.5.0)
+      ast (~> 2.4.1)
+      racc
+    public_suffix (6.0.1)
+    racc (1.8.1)
+    rainbow (3.1.1)
+    rake (13.2.1)
+    regexp_parser (2.9.2)
+    rexml (3.3.8)
+    rspec (3.13.0)
+      rspec-core (~> 3.13.0)
+      rspec-expectations (~> 3.13.0)
+      rspec-mocks (~> 3.13.0)
+    rspec-core (3.13.1)
+      rspec-support (~> 3.13.0)
+    rspec-expectations (3.13.3)
+      diff-lcs (>= 1.2.0, < 2.0)
+      rspec-support (~> 3.13.0)
+    rspec-mocks (3.13.2)
+      diff-lcs (>= 1.2.0, < 2.0)
+      rspec-support (~> 3.13.0)
+    rspec-support (3.13.1)
+    rubocop (1.66.1)
+      json (~> 2.3)
+      language_server-protocol (>= 3.17.0)
+      parallel (~> 1.10)
+      parser (>= 3.3.0.2)
+      rainbow (>= 2.2.2, < 4.0)
+      regexp_parser (>= 2.4, < 3.0)
+      rubocop-ast (>= 1.32.2, < 2.0)
+      ruby-progressbar (~> 1.7)
+      unicode-display_width (>= 2.4.0, < 3.0)
+    rubocop-ast (1.32.3)
+      parser (>= 3.3.1.0)
+    ruby-progressbar (1.13.0)
+    unicode-display_width (2.6.0)
+    vcr (6.3.1)
+      base64
+    webmock (3.24.0)
+      addressable (>= 2.8.0)
+      crack (>= 0.3.2)
+      hashdiff (>= 0.4.0, < 2.0.0)
+
+PLATFORMS
+  arm64-darwin-23
+  ruby
+
+DEPENDENCIES
+  minitest (~> 5.16)
+  rake (~> 13.0)
+  rspec
+  rubocop (~> 1.21)
+  themoviedb!
+  vcr
+  webmock
+
+BUNDLED WITH
+   2.5.20

themoviedb.gemspec

@@ -1,5 +1,4 @@
-# -*- encoding: utf-8 -*-
-lib = File.expand_path('../lib', __FILE__)
+lib = File.expand_path('lib', __dir__)
 $LOAD_PATH.unshift(lib) unless $LOAD_PATH.include?(lib)
 
 require 'themoviedb/version'
@@ -18,9 +17,4 @@ Gem::Specification.new do |s|
   s.require_paths = ['lib']
 
   s.add_runtime_dependency 'httparty'
-
-  s.add_development_dependency 'vcr'
-  s.add_development_dependency 'rake'
-  s.add_development_dependency 'rspec'
-  s.add_development_dependency 'webmock'
 end