widget/material: clean up package docs, add license, rename file

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

widget/material/button.go

@@ -1,6 +1,5 @@
 // SPDX-License-Identifier: Unlicense OR MIT
 
-// Package material implements the Material design.
 package material
 
 import (

widget/material/checkable.go

@@ -1,3 +1,5 @@
+// SPDX-License-Identifier: Unlicense OR MIT
+
 package material
 
 import (

widget/material/checkbox.go

@@ -1,6 +1,5 @@
 // SPDX-License-Identifier: Unlicense OR MIT
 
-// Package material implements the Material design.
 package material
 
 import (

widget/material/doc.go

@@ -11,12 +11,12 @@
 //
 // This snippet defines a button that prints a message when clicked:
 //
-// 	  var gtx *layout.Context
-//    button := new(widget.Button)
+//     var gtx *layout.Context
+//     button := new(widget.Button)
 //
-//    for button.Clicked(gtx) {
-//        fmt.Println("Clicked!")
-// 	  }
+//     for button.Clicked(gtx) {
+//         fmt.Println("Clicked!")
+//     }
 //
 // Use a Theme to draw the button:
 //
@@ -24,26 +24,28 @@
 //
 //     th.Button("Click me!").Layout(gtx, button)
 //
+// Customization
+//
 // Quite often, a program needs to customize the theme provided defaults. Several
 // options are available, depending on the nature of the change:
 //
-// - Mandatory parameters. Some parameters are not part of the widget state but
+// Mandatory parameters: Some parameters are not part of the widget state but
 // have no obvious default. In the program above, the button text is a
 // parameter to the Theme.Button method.
 //
-// - Theme-global parameters. For changing the look of all widgets drawn with a
+// Theme-global parameters: For changing the look of all widgets drawn with a
 // particular theme, adjust the `Theme` fields:
 //
 //     theme.Color.Primary = color.RGBA{...}
 //
-// - Widget-local parameters. For changing the look of a particular widget,
+// Widget-local parameters: For changing the look of a particular widget,
 // adjust the widget specific theme object:
 //
 //     btn := th.Button("Click me!")
 //     btn.Font.Style = text.Italic
 //     btn.Layout(gtx)
 //
-// - Widget variants. A widget can have several distinct representations even
+// Widget variants: A widget can have several distinct representations even
 // though the underlying state is the same. A widget.Button can be drawn as a
 // round icon button:
 //
@@ -51,7 +53,7 @@
 //
 //     th.IconButton(icon).Layout(gtx, button)
 //
-// - Specialized widgets. Theme both define a generic Label method
+// Specialized widgets: Theme both define a generic Label method
 // that takes a text size, and specialized methods for standard text
 // sizes such as Theme.H1 and Theme.Body2.
 package material

widget/material/icon.go

@@ -1,6 +1,5 @@
 // SPDX-License-Identifier: Unlicense OR MIT
 
-// Package material implements the Material design.
 package material
 
 import (

widget/material/radiobutton.go

@@ -1,6 +1,5 @@
 // SPDX-License-Identifier: Unlicense OR MIT
 
-// Package material implements the Material design.
 package material
 
 import (