Allow end user to configure what ports to listen on

sunshine/main.h

@@ -29,6 +29,8 @@ void print_help(const char *name);
 std::string read_file(const char *path);
 int write_file(const char *path, const std::string_view &contents);
 
+std::uint16_t map_port(int port);
+
 namespace mail {
 #define MAIL(x) \
   constexpr auto x = std::string_view { #x }