internal/ed25519: add TODO note and doc ref

internal/edwards25519/edwards25519.go

@@ -22,6 +22,10 @@ var D2 = new(radix51.FieldElement).Add(D, D)
 
 // Point types.
 
+// TODO: write documentation
+// TODO: rename (T,X,Y,Z) to (W0,W1,W2,W3) for P2 and P3 models?
+// https://doc-internal.dalek.rs/curve25519_dalek/backend/serial/curve_models/index.html
+
 type ProjP1xP1 struct {
 	X, Y, Z, T radix51.FieldElement
 }