Add minetest.get_game_info and allow reading game.conf (#12989)

Co-authored-by: sfan5 <sfan5@live.de>

doc/lua_api.txt

@@ -4879,6 +4879,18 @@ Utilities
   or checking if a mod is enabled.
 * `minetest.get_modnames()`: returns a list of enabled mods, sorted alphabetically.
     * Does not include disabled mods, even if they are installed.
+* `minetest.get_game_info()`: returns a table containing information about the
+  current game. Note that other meta information (e.g. version/release number)
+  can be manually read from `game.conf` in the game's root directory.
+
+      {
+          id = string,
+          title = string,
+          author = string,
+          -- The root directory of the game
+          path = string,
+      }
+
 * `minetest.get_worldpath()`: returns e.g. `"/home/user/.minetest/world"`
     * Useful for storing custom data
 * `minetest.is_singleplayer()`