chore: exclude mocks and fixtures from bundle (#8801)

Author: jordanl17

packages/sanity/package.json

@@ -126,6 +126,8 @@
     "static",
     "!**/__test__/**",
     "!**/__tests__/**",
+    "!**/__mocks__/**",
+    "!**/__fixtures__/**",
     "!**/__workshop__/**",
     "desk.js",
     "presentation.js",