Define path with __dir__

Inspired by https://bogdanvlviv.github.io/posts/ruby/with-__dir__-we-can-restore-order-in-the-universe.html

jekyll-algolia.gemspec

@@ -1,4 +1,4 @@
-require File.join(File.dirname(__FILE__), 'lib/jekyll/algolia/version.rb')
+require File.join(__dir__, 'lib/jekyll/algolia/version.rb')
 
 Gem::Specification.new do |gem|
   # Required attributes

lib/jekyll/algolia/logger.rb

@@ -40,7 +40,7 @@ module Jekyll
       def self.known_message(message_id, metadata = {})
         file = File.expand_path(
           File.join(
-            File.dirname(__FILE__), '../../..', 'errors', "#{message_id}.txt"
+            __dir__, '../..', 'errors', "#{message_id}.txt"
           )
         )