add(widget/Spacer): empty widget implementation

src/widget/Spacer.zig

@@ -0,0 +1,33 @@
+const std = @import("std");
+const terminal = @import("../terminal.zig");
+
+const isTaggedUnion = @import("../event.zig").isTaggedUnion;
+const Error = @import("../event.zig").Error;
+
+const log = std.log.scoped(.widget_spacer);
+
+pub fn Widget(comptime Event: type) type {
+    if (!isTaggedUnion(Event)) {
+        @compileError("Provided user event `Event` for `Layout(comptime Event: type)` is not of type `union(enum)`.");
+    }
+    return struct {
+        pub fn init() @This() {
+            return .{};
+        }
+
+        pub fn deinit(this: *@This()) void {
+            this.* = undefined;
+        }
+
+        pub fn handle(this: *@This(), event: Event) ?Event {
+            _ = this;
+            _ = event;
+            return null;
+        }
+
+        pub fn content(this: *@This()) ![]u8 {
+            _ = this;
+            return &[0]u8{};
+        }
+    };
+}