example/zig-formatter: show how to use formatters from libghostty (#9407)

.github/workflows/test.yml

@@ -95,7 +95,15 @@ jobs:
       fail-fast: false
       matrix:
         dir:
-          [c-vt, c-vt-key-encode, c-vt-paste, c-vt-sgr, zig-vt, zig-vt-stream]
+          [
+            c-vt,
+            c-vt-key-encode,
+            c-vt-paste,
+            c-vt-sgr,
+            zig-formatter,
+            zig-vt,
+            zig-vt-stream,
+          ]
     name: Example ${{ matrix.dir }}
     runs-on: namespace-profile-ghostty-sm
     needs: test