Added helper functions in package text

This package adds back the Plain function from the old package text as
well as a new function called SolidColor that returns a new RGBA color
with the alpha bits maxed out.

These functions are there for convenience. They're also outside the
scope of the code generator and repository.

text/text_extras.go

@@ -0,0 +1,12 @@
+package text
+
+// Plain creates a new text.Rich without any formatting segments.
+func Plain(text string) Rich {
+	return Rich{Content: text}
+}
+
+// SolidColor takes in a 24-bit RGB color and overrides the alpha bits with
+// 0xFF, making the color solid.
+func SolidColor(rgb uint32) uint32 {
+	return rgb | (0xFF << 24)
+}