fix(build): ensure Klogger::VERSION is set correctly in built gems

This requires "klogger/version" by default, and also includes any
VERSION from in the repository when building the gem, to ensure that
"Klogger::VERSION" has the correct value. Previously it would always end
up returning "0.0.0.dev".

.gitignore

@@ -1,2 +1 @@
 Gemfile.lock
-VERSION

klogger-logger.gemspec

@@ -10,7 +10,8 @@ Gem::Specification.new do |s|
   s.required_ruby_version = '>= 2.6'
   s.homepage      = 'https://github.com/krystal/klogger'
   s.version       = Klogger::VERSION
-  s.files         = Dir.glob('{lib}/**/*')
+  s.files         = Dir.glob(File.join('{lib}', '**', '*')) +
+                    Dir['{README.*,*LICENSE*,VERSION}']
   s.require_paths = ['lib']
   s.authors       = ['Adam Cooke']
   s.email         = ['adam@krystal.uk']

lib/klogger/logger.rb

@@ -2,11 +2,14 @@
 
 require 'logger'
 require 'securerandom'
+
+require 'concurrent/atomic/thread_local_var'
+
 require 'klogger/formatters/json'
 require 'klogger/formatters/simple'
 require 'klogger/formatters/go'
-require 'concurrent/atomic/thread_local_var'
 require 'klogger/group_set'
+require 'klogger/version'
 
 module Klogger
   class Logger < ::Logger