docs: documentation for unicode_emoji namespace (#739)

buildtools/emojis.php

@@ -2,10 +2,28 @@
 
 echo "-- Autogenrating include/dpp/unicode_emoji.h\n";
 
-$header = "#pragma once\n\nnamespace dpp { namespace unicode_emoji {\n";
+$url = "https://raw.githubusercontent.com/ArkinSolomon/discord-emoji-converter/master/emojis.json";
+
+$header = <<<END
+#pragma once
+
+namespace dpp {
+
+/**
+ * The unicode emojis in this namespace are auto-generated from {$url}
+ *
+ * If you want to use this, you have to pull the header in separately. e.g.
+ * ```cpp
+ * #include <dpp/dpp.h>
+ * #include <dpp/unicode_emoji.h>
+ * ```
+ */
+namespace unicode_emoji {
+
+END;
 
 /* This JSON is generated originally via the NPM package maintained by Discord themselves at https://www.npmjs.com/package/discord-emoji */
-$emojis = json_decode(file_get_contents("https://raw.githubusercontent.com/ArkinSolomon/discord-emoji-converter/master/emojis.json"));
+$emojis = json_decode(file_get_contents($url));
 if ($emojis) {
     foreach ($emojis as $name=>$code) {
         if (preg_match("/^\d+/", $name)) {