Add debug gem in development

This helped me debug a thing in the upcoming change! It lets you drop a
`debugger` line into the app, then run `rdbg --attach` in another
terminal to get into a debug session. Neat!

Gemfile

@@ -66,7 +66,10 @@ gem "async-http", "~> 0.75.0", require: false
 gem "thread-local", "~> 1.1", require: false
 
 # For debugging.
-gem 'web-console', '~> 4.2', group: :development
+group :development do
+	gem 'debug', '~> 1.9.2'
+	gem 'web-console', '~> 4.2'
+end
 
 # Reduces boot times through caching; required in config/boot.rb
 gem 'bootsnap', '~> 1.16', require: false

Gemfile.lock

@@ -134,6 +134,9 @@ GEM
     crass (1.0.6)
     csv (3.3.0)
     date (3.3.4)
+    debug (1.9.2)
+      irb (~> 1.10)
+      reline (>= 0.3.8)
     devise (4.9.4)
       bcrypt (~> 3.0)
       orm_adapter (~> 0.1)
@@ -521,6 +524,7 @@ DEPENDENCIES
   async (~> 2.17)
   async-http (~> 0.75.0)
   bootsnap (~> 1.16)
+  debug (~> 1.9.2)
   devise (~> 4.9, >= 4.9.2)
   devise-encryptable (~> 0.2.0)
   dotenv-rails (~> 2.8, >= 2.8.1)