update docs

examples/software/hello/void/files/hello.c

@@ -0,0 +1,6 @@
+#include <stdio.h>
+int main(int argc, char **argv) {
+    printf("Hello from an FDS AArch64 software cartridge%s%s\n",
+           argc > 1 ? ": " : "", argc > 1 ? argv[1] : "");
+    return 0;
+}

examples/software/hello/void/template

@@ -0,0 +1,15 @@
+# Small example of a native Void source package, cross-built by xbps-src.
+pkgname=fds-demo-hello
+version=1.0
+revision=1
+archs="aarch64"
+short_desc="FDS cartridge hello example"
+maintainer="FDS/OS maintainers"
+license="MIT"
+homepage="https://docs.voidlinux.org/xbps/"
+do_build() {
+	${CC} ${CFLAGS} "${FILESDIR}/hello.c" ${LDFLAGS} -o hello
+}
+do_install() {
+	vbin hello
+}