add deprecation warning

Cargo.lock

@@ -420,7 +420,7 @@ dependencies = [
 
 [[package]]
 name = "servicepoint2"
-version = "0.4.2"
+version = "0.4.3"
 dependencies = [
  "bzip2",
  "flate2",

README.md

@@ -1,3 +1,17 @@
+# Archived!
+
+This fork will no longer be the repository where releases are published.
+
+Please switch to the [upstreamed version](https://github.com/cccb/servicepoint) with the following changes in your Cargo.toml:
+
+```diff
+[dependencies]
+- servicepoint2 = "0.4.2"
++ servicepoint = "0.5.0"
+```
+
+The new crate is also published on [crates.io](https://crates.io/crates/servicepoint).
+
 # servicepoint2
 
 [![crates.io](https://img.shields.io/crates/v/servicepoint2.svg)](https://crates.io/crates/servicepoint2)

servicepoint2/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "servicepoint2"
-version = "0.4.2"
+version = "0.4.3"
 publish = true
 edition = "2021"
 license = "GPL-3.0-or-later"

servicepoint2/build.rs

@@ -0,0 +1,3 @@
+pub fn main() {
+    println!("cargo:warning=This crate is unmaintained. Please switch to `servicepoint`.")
+}