docs: add basic code samples

examples/simple-default.zig

@@ -0,0 +1,33 @@
+//! Minimal nightwatch example: watch the current directory with the
+//! platform default backend and print every event to stderr.
+//!
+//! Build and run (from this directory):
+//!
+//!   zig build-exe --dep nightwatch -Msimple-default=simple-default.zig -Mnightwatch=../src/nightwatch.zig
+//!   ./simple-default
+
+const nightwatch = @import("nightwatch");
+const std = @import("std");
+
+const H = struct {
+    handler: nightwatch.Default.Handler,
+
+    const vtable = nightwatch.Default.Handler.VTable{ .change = change, .rename = rename };
+
+    fn change(_: *nightwatch.Default.Handler, path: []const u8, event: nightwatch.EventType, _: nightwatch.ObjectType) error{HandlerFailed}!void {
+        std.debug.print("{s}  {s}\n", .{ @tagName(event), path });
+    }
+
+    fn rename(_: *nightwatch.Default.Handler, src: []const u8, dst: []const u8, _: nightwatch.ObjectType) error{HandlerFailed}!void {
+        std.debug.print("rename  {s}  ->  {s}\n", .{ src, dst });
+    }
+};
+
+pub fn main() !void {
+    const allocator = std.heap.page_allocator;
+    var h = H{ .handler = .{ .vtable = &H.vtable } };
+    var watcher = try nightwatch.Default.init(allocator, &h.handler);
+    defer watcher.deinit();
+    try watcher.watch(".");
+    std.Thread.sleep(std.time.ns_per_s * 60);
+}