Update wrangling docs to link to SwiftShader roller.

Bug: angleproject:1944
Change-Id: I8eabf5e8ec5cd7bfeab4db9b7bd5422f5168744e
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1880159
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>

infra/ANGLEWrangling.md

@@ -77,11 +77,12 @@ Chrome with the latest ANGLE changes.
 
 We also use additional auto-rollers to roll third party libraries into ANGLE once per day:
 
- * [SPIRV-Headers into ANGLE](https://autoroll.skia.org/r/spirv-headers-angle-autoroll),
- * [SPIRV-Tools into ANGLE](https://autoroll.skia.org/r/spirv-tools-angle-autoroll) and
- * [glslang into ANGLE](https://autoroll.skia.org/r/glslang-angle-autoroll)
+ * [SPIRV-Tools into ANGLE](https://autoroll.skia.org/r/spirv-tools-angle-autoroll),
+ * [glslang into ANGLE](https://autoroll.skia.org/r/glslang-angle-autoroll) and
+ * [SwiftShader into ANGLE](https://autoroll.skia.org/r/swiftshader-angle-autoroll)
 
-Please ensure these rollers are also healthy and unblocked.
+Please ensure these rollers are also healthy and unblocked. You can trigger manual rolls using the dashboards
+to land high-priority changes.
 
 ## Task 4: ANGLE Standalone Testing