Add Greek translation (#248)

Author: lysnikolaou

config.toml

@@ -15,6 +15,10 @@ sphinxopts = [
     "-D latex_elements.fontenc=",
 ]
 
+[languages.el]
+name = "Greek"
+translated_name = "Ελληνικά"
+
 [languages.en]
 name = "English"