text: add android portability notice to NewShaper

NewShaper cannot be called prior to opening an application window on Android unless
the application does not want system font support. Add a note to this effect to the
constructor.

Signed-off-by: Chris Waldon <christopher.waldon.dev@gmail.com>

text/shaper.go

@@ -245,8 +245,11 @@ func WithCollection(collection []FontFace) ShaperOption {
 	}
 }
 
-// NewShaper constructs a shaper with the provided collection of font faces
-// available.
+// NewShaper constructs a shaper with the provided options.
+//
+// NewShaper must be called after [app.NewWindow], unless the [NoSystemFonts]
+// option is specified. This is an unfortunate restriction caused by some platforms
+// such as Android.
 func NewShaper(options ...ShaperOption) *Shaper {
 	l := &Shaper{}
 	for _, opt := range options {