Doxygen support (#43)

* init doxygen

* fix format

* use readme as main file

* don't generate LaTeX

* automatically use correct project version and update html settings

* minify Doxyfile

* add documentation

* add workflow to publish documentation

* remove mac comment

* formatting

* fix typo

* grammar

include/greeter.h

@@ -4,13 +4,27 @@
 
 namespace greeter {
 
+  /**  Language codes to be used with the Greeter class */
   enum class LanguageCode { EN, DE, ES, FR };
 
+  /**
+   * A class for saying hello in multiple languages
+   */
   class Greeter {
     std::string name;
 
   public:
+    /**
+     * Creates a new greeter
+     * @param name the name to greet
+     */
     Greeter(std::string name);
+
+    /**
+     * Creates a localized string containing the greeting
+     * @param lang the language to greet in
+     * @return a string containing the greeting
+     */
     std::string greet(LanguageCode lang = LanguageCode::EN) const;
   };