Add library collection `vendor`

src/main.cpp

@@ -2024,6 +2024,7 @@ int main(int arg_count, char const **arg_ptr) {
 	array_init(&library_collections, heap_allocator());
 	// NOTE(bill): 'core' cannot be (re)defined by the user
 	add_library_collection(str_lit("core"), get_fullpath_relative(heap_allocator(), odin_root_dir(), str_lit("core")));
+	add_library_collection(str_lit("vendor"), get_fullpath_relative(heap_allocator(), odin_root_dir(), str_lit("vendor")));
 
 	map_init(&build_context.defined_values, heap_allocator());
 	build_context.extra_packages.allocator = heap_allocator();