example: rename apps module

The new name emphasize the nature of the programs and won't be
confused with package `app`.

Signed-off-by: Elias Naur <mail@eliasnaur.com>

example/hello/hello.go

@@ -0,0 +1,61 @@
+// SPDX-License-Identifier: Unlicense OR MIT
+
+package main
+
+// A simple Gio program. See https://gioui.org for more information.
+
+import (
+	"image/color"
+	"log"
+
+	"gioui.org/app"
+	"gioui.org/layout"
+	"gioui.org/op"
+	"gioui.org/op/paint"
+	"gioui.org/text"
+	"gioui.org/text/shape"
+	"gioui.org/unit"
+
+	"golang.org/x/image/font/gofont/goregular"
+	"golang.org/x/image/font/sfnt"
+)
+
+func main() {
+	go func() {
+		w := app.NewWindow()
+		if err := loop(w); err != nil {
+			log.Fatal(err)
+		}
+	}()
+	app.Main()
+}
+
+func loop(w *app.Window) error {
+	regular, err := sfnt.Parse(goregular.TTF)
+	if err != nil {
+		panic("failed to load font")
+	}
+	family := &shape.Family{
+		Regular: regular,
+	}
+	maroon := color.RGBA{127, 0, 0, 255}
+	message := "Hello, Gio"
+	gtx := &layout.Context{
+		Queue: w.Queue(),
+	}
+	for {
+		e := <-w.Events()
+		switch e := e.(type) {
+		case app.DestroyEvent:
+			return e.Err
+		case app.UpdateEvent:
+			gtx.Reset(&e.Config, e.Size)
+			var material op.MacroOp
+			material.Record(gtx.Ops)
+			paint.ColorOp{Color: maroon}.Add(gtx.Ops)
+			material.Stop()
+			text.Label{Material: material, Size: unit.Sp(72), Alignment: text.Middle, Text: message}.Layout(gtx, family)
+			w.Update(gtx.Ops)
+		}
+	}
+}