mach: fundamental changes

- Core doesn't depend to `App` anymore
 - `setOptions` has replaced with some new functions (`setTitle`,
   `setSize`, etc)
   - and more

src/platform/wasm/Timer.zig

@@ -0,0 +1,25 @@
+const std = @import("std");
+const js = @import("js.zig");
+
+pub const Timer = @This();
+
+initial: f64 = undefined,
+
+pub fn start() !Timer {
+    return Timer{ .initial = js.machPerfNow() };
+}
+
+pub fn read(timer: *Timer) u64 {
+    return (js.machPerfNow() - timer.initial) * std.time.ns_per_ms;
+}
+
+pub fn reset(timer: *Timer) void {
+    timer.initial = js.machPerfNow();
+}
+
+pub fn lap(timer: *Timer) u64 {
+    const now = js.machPerfNow();
+    const initial = timer.initial;
+    timer.initial = now;
+    return @floatToInt(u64, now - initial) * std.time.ns_per_ms;
+}