Ruby: Ignore .irb_history file

This file is created locally by IRB to store the last 1,000 commands

It doesn't make sense to keep this history in the repository.

https://ruby-doc.org/stdlib-2.4.0/libdoc/irb/rdoc/IRB.html#module-IRB-label-History

Ruby.gitignore

@@ -13,8 +13,9 @@
 # Used by dotenv library to load environment variables.
 # .env
 
-# Ignore Byebug command history file.
+# Ignore Byebug/IRB command history files.
 .byebug_history
+.irb_history
 
 ## Specific to RubyMotion:
 .dat*