Add --version lowercase flag to comply with convention

README.md

@@ -130,7 +130,7 @@ openFPGALoader -- a program to flash FPGA
   -X, --read-xadc               Read XADC (Xilinx FPGA only)
       --read-register arg       Read Status Register(Xilinx FPGA only)
       --user-flash arg          User flash file (Gowin LittleBee FPGA only)
-  -V, --Version                 Print program version
+  -V, --Version, --version      Print program version
 
 Mandatory or optional arguments to long options are also mandatory or optional
 for any corresponding short options.

src/main.cpp

@@ -1027,7 +1027,7 @@ int parse_opt(int argc, char **argv, struct arguments *args,
 				cxxopts::value<std::string>(args->read_register))
 			("user-flash", "User flash file (Gowin LittleBee FPGA only)",
 				cxxopts::value<std::string>(args->user_flash))
-			("V,Version", "Print program version");
+			("V,Version,version", "Print program version");
 
 		options.parse_positional({"bitstream"});
 		auto result = options.parse(argc, argv);