examples: Add an example that uses the dirCreateFile mock

examples/open_file.zig

@@ -0,0 +1,25 @@
+const std = @import("std");
+const Io = std.Io;
+
+const Simulator = @import("zigmulator");
+
+fn createFileProgram(init: std.process.Init) anyerror!void {
+    const file = try Io.Dir.cwd().createFile(init.io, "message.txt", .{});
+
+    var writer = file.writerStreaming(init.io, &.{});
+    try writer.interface.writeAll("created through dirCreateFile");
+    try writer.interface.flush();
+}
+
+pub fn main(init: std.process.Init) !void {
+    var sim: Simulator = undefined;
+    sim.init(std.heap.page_allocator, init.io);
+    defer sim.deinit();
+
+    try sim.addExecutable("create_file", createFileProgram);
+    try sim.spawn("create_file", .{});
+
+    while (sim.scheduleOne()) {}
+
+    sim.dumpFiles();
+}