ci: Add check for formatting `default.json` (#30034)

Marshall Bowers created 

This PR adds a check in CI to ensure that `assets/settings/default.json`
is formatted consistently.

Release Notes:

- N/A

Change summary

.github/workflows/ci.yml | 12 +++++++++++-
.prettierrc              |  3 +++
docs/.prettierrc         |  3 +++
3 files changed, 17 insertions(+), 1 deletion(-)

Detailed changes

.github/workflows/ci.yml 🔗 

@@ -162,13 +162,23 @@ jobs:
         working-directory: ./docs
         run: |
           pnpm dlx prettier@${PRETTIER_VERSION} . --check || {
-            echo "To fix, run from the root of the zed repo:"
+            echo "To fix, run from the root of the Zed repo:"
             echo "  cd docs && pnpm dlx prettier@${PRETTIER_VERSION} . --write && cd .."
             false
           }
         env:
           PRETTIER_VERSION: 3.5.0
 
+      - name: Prettier Check on default.json
+        run: |
+          pnpm dlx prettier@${PRETTIER_VERSION} assets/settings/default.json --check || {
+            echo "To fix, run from the root of the Zed repo:"
+            echo "  pnpm dlx prettier@${PRETTIER_VERSION} assets/settings/default.json --write"
+            false
+          }
+        env:
+          PRETTIER_VERSION: 3.5.0
+
       # To support writing comments that they will certainly be revisited.
       - name: Check for todo! and FIXME comments
         run: script/check-todos