Add deprecation note to README (#180)

See equivalent in Masonry

linebender/masonry#60

Author: DJMcNab

README.md

@@ -1,3 +1,8 @@
+> [!Important]
+> Linebender no longer uses Glazier, and so this project is no longer supported.
+>
+> You should prefer to use [winit](https://crates.io/crates/winit) instead.
+
 <div align="center">
 
 # glazier
@@ -11,6 +16,16 @@
 
 </div>
 
+> [!Caution]
+> This README content has not been validated recently.
+>
+> Glazier is no longer supported, and should not be used.
+>
+> This repository is made available for reference purposes.
+>
+> Feel free to use the [#glazier channel](https://xi.zulipchat.com/#narrow/stream/351333-glazier) if reusing code from Glazier.
+> Some of the text input handling code is more complete than the equivalent in winit, and so might be useful for reference.
+
 Glazier is an operating system integration layer infrastructure layer intended for
 high quality GUI toolkits in Rust. It is agnostic to the choice of drawing, so the
 client must provide that, but the goal is to abstract over most of the other