text/shape: move package measure

Text shaping is a common name for what package measure does. Rename
it to "shape" and move it below the text package.

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

text/shape/measure.go

@@ -1,9 +1,9 @@
 // SPDX-License-Identifier: Unlicense OR MIT
 
 /*
-Package measure implements text layout and shaping.
+Package shape implements text layout and shaping.
 */
-package measure
+package shape
 
 import (
 	"math"

text/shape/opentype.go

@@ -1,6 +1,6 @@
 // SPDX-License-Identifier: Unlicense OR MIT
 
-package measure
+package shape
 
 import (
 	"golang.org/x/image/font"