chore: deprecate types and readme

README.md

@@ -0,0 +1,7 @@
+## ❗ This repo is no longer maintained.
+👉 We highly recommend switching to the maintained version at https://github.com/ipfs/boxo/tree/main/verifcid.
+🏎️ Good news!  There is [tooling and documentation](https://github.com/ipfs/boxo#migrating-to-boxo) to expedite a switch in your repo. 
+
+⚠️ If you continue using this repo, please note that security fixes will not be provided (unless someone steps in to maintain it).
+
+📚 Learn more, including how to take the maintainership mantle or ask questions, [here](https://github.com/ipfs/boxo/wiki/Copied-or-Migrated-Repos-FAQ).

validate.go

@@ -7,8 +7,13 @@ import (
 	mh "github.com/multiformats/go-multihash"
 )
 
+// Deprecated: use github.com/ipfs/boxo/verifcid.ErrPossiblyInsecureHashFunction
 var ErrPossiblyInsecureHashFunction = fmt.Errorf("potentially insecure hash functions not allowed")
+
+// Deprecated: use github.com/ipfs/boxo/verifcid.ErrBelowMinimumHashLength
 var ErrBelowMinimumHashLength = fmt.Errorf("hashes must be at least %d bytes long", minimumHashLength)
+
+// Deprecated: use github.com/ipfs/boxo/verifcid.ErrAboveMaximumHashLength
 var ErrAboveMaximumHashLength = fmt.Errorf("hashes must be at most %d bytes long", maximumHashLength)
 
 const minimumHashLength = 20
@@ -36,6 +41,7 @@ var goodset = map[uint64]bool{
 	mh.SHA1: true, // not really secure but still useful
 }
 
+// Deprecated: use github.com/ipfs/boxo/verifcid.IsGoodHash
 func IsGoodHash(code uint64) bool {
 	good, found := goodset[code]
 	if good {
@@ -54,6 +60,7 @@ func IsGoodHash(code uint64) bool {
 	return false
 }
 
+// Deprecated: use github.com/ipfs/boxo/verifcid.ValidateCid
 func ValidateCid(c cid.Cid) error {
 	pref := c.Prefix()
 	if !IsGoodHash(pref.MhType) {