require version when loading gem

Apps and other gems (like lookbook) want to be able to easily tell whether they are working with Phlex v1 or v2, and lookbook is now trying to check `Phlex::VERSION` for that, which is not loaded by default.

Signed-off-by: Mark Oleson <fusion2004@gmail.com>

Author: fusion2004

lib/phlex.rb

@@ -3,6 +3,7 @@
 require "erb"
 require "set"
 require "zeitwerk"
+require "phlex/version"
 
 module Phlex
 	Loader = Zeitwerk::Loader.for_gem.tap do |loader|