Move zigsdof code to subdirectory

zigsdof/src/io.zig

@@ -25,7 +25,7 @@ pub fn jsonFileToSimConfig(
     io: std.Io,
 ) !drone.QuadCopterSim {
     const cwd = std.Io.Dir.cwd();
-    const file = try cwd.openFile(io, file_path, .{ .mode = .read_only });
+    cons file = try cwd.openFile(io, file_path, .{ .mode = .read_only });
     defer file.close(io);
 
     var file_reader = file.reader(io, &.{});

zigsdof/src/main.zig

@@ -7,3 +7,11 @@ test "main" {
     _ = @import("./integration.zig");
     _ = @import("./io.zig");
 }
+
+test "how ptrs work" {
+    var ptr: *usize = 0;
+    var val = 1;
+    ptr = val;
+    val = 2;
+    std.testing.expect(*ptr == 1);
+}