feat(progress): make full/empty fill characters configurable

progress/progress.go

@@ -79,6 +79,14 @@ func WithSolidFill(color string) Option {
 	}
 }
 
+// WithCustomFillCharacters sets the characters used to construct the full and empty components of the progress bar.
+func WithCustomFillCharacters(full rune, empty rune) Option {
+	return func(m *Model) {
+		m.Full = full
+		m.Empty = empty
+	}
+}
+
 // WithoutPercentage hides the numeric percentage.
 func WithoutPercentage() Option {
 	return func(m *Model) {