Update README.md

Author: Jarred-Sumner

README.md

@@ -28,6 +28,16 @@ If you need to authenticate with a private registry, you can set the `BUN_AUTH_T
   run: bun install --frozen-lockfile
 ```
 
+### Override download url
+
+If you need to override the download URL, you can use the `bun-download-url` input.
+
+```yaml
+- uses: oven-sh/setup-bun
+  with:
+    bun-download-url: "https://github.com/oven-sh/bun/releases/latest/download/bun-linux-x64.zip"
+```
+
 ### Node.js not needed
 
 In most cases, you shouldn't need to use the [setup-node](https://github.com/actions/setup-node) GitHub Action.