Use the new Zulip name (Linebender rather than Xi) (#506)

Use new style of Zulip mention

README.md

@@ -4,7 +4,7 @@
 
 **An experimental GPU compute-centric 2D renderer**
 
-[![Xi Zulip](https://img.shields.io/badge/Xi%20Zulip-%23gpu-blue?logo=Zulip)](https://xi.zulipchat.com/#narrow/stream/197075-gpu)
+[![Linebender Zulip](https://img.shields.io/badge/Linebender-%23gpu-blue?logo=Zulip)](https://xi.zulipchat.com/#narrow/stream/197075-gpu)
 [![dependency status](https://deps.rs/repo/github/linebender/vello/status.svg)](https://deps.rs/repo/github/linebender/vello)
 [![MIT/Apache 2.0](https://img.shields.io/badge/license-MIT%2FApache-blue.svg)](#license)
 [![wgpu version](https://img.shields.io/badge/wgpu-v0.19.3-orange.svg)](https://crates.io/crates/wgpu)
@@ -231,7 +231,7 @@ VELLO_STATIC_LOG="vello=trace" VELLO_STATIC_ARGS="--test-scenes" cargo apk run -
 
 ## Community
 
-Discussion of Vello development happens in the [Xi Zulip](https://xi.zulipchat.com/), specifically the [#gpu stream](https://xi.zulipchat.com/#narrow/stream/197075-gpu). All public content can be read without logging in.
+Discussion of Vello development happens in the [Linebender Zulip](https://xi.zulipchat.com/), specifically the [#gpu stream](https://xi.zulipchat.com/#narrow/stream/197075-gpu). All public content can be read without logging in.
 
 Contributions are welcome by pull request. The [Rust code of conduct] applies.