Update help text to redirect to new online docs

src/asm/main.c

@@ -323,7 +323,7 @@ static void print_usage(void)
 "    -V, --version            print RGBASM version and exit\n"
 "    -W, --warning <warning>  enable or disable warnings\n"
 "\n"
-"For help, use `man rgbasm' or go to https://rednex.github.io/rgbds/\n",
+"For help, use `man rgbasm' or go to https://rgbds.gbdev.io/docs/\n",
 	      stderr);
 	exit(1);
 }

src/fix/main.c

@@ -63,7 +63,7 @@ static void print_usage(void)
 "    -V, --version               print RGBFIX version and exit\n"
 "    -v, --validate              fix the header logo and both checksums (-f lhg)\n"
 "\n"
-"For help, use `man rgbfix' or go to https://rednex.github.io/rgbds/\n",
+"For help, use `man rgbfix' or go to https://rgbds.gbdev.io/docs/\n",
 	      stderr);
 	exit(1);
 }

src/gfx/main.c

@@ -66,7 +66,7 @@ static void print_usage(void)
 "    -u, --unique-tiles        optimize out identical tiles\n"
 "    -V, --version             print RGBGFX version and exit\n"
 "\n"
-"For help, use `man rgbgfx' or go to https://rednex.github.io/rgbds/\n",
+"For help, use `man rgbgfx' or go to https://rgbds.gbdev.io/docs/\n",
 	      stderr);
 	exit(1);
 }

src/link/main.c

@@ -132,7 +132,7 @@ static void printUsage(void)
 "    -x, --nopad                disable padding of output binary\n"
 "    -V, --version              print RGBLINK version and exits\n"
 "\n"
-"For help, use `man rgblink' or go to https://rednex.github.io/rgbds/\n",
+"For help, use `man rgblink' or go to https://rgbds.gbdev.io/docs/\n",
 	      stderr);
 }