feat(hello): add a Hellorld application

just the docs example, but better commented

code/hellorld/hello.c

@@ -0,0 +1,16 @@
+/*
+ * hello.c
+ *
+ * Hellorld application using Psion's "CLIB" - just plain C, no Psion extensions
+ */
+
+#include <stdio.h>
+
+int main(VOID) {
+	// Does sprintf work here? The SDK is probably too old, but modern conventions would be nice
+	printf("Hellorld!");
+	// Wait for a key to be pressed
+	getchar();
+	// Exit, not sure why 0 is being passed as it's a void? But this is the SDK example code
+	return(0);
+}

code/hellorld/hello.pr

@@ -0,0 +1,5 @@
+#system epoc img
+#model small jpi
+
+#compile hello
+#link hello