Read JSON (#1081)

Fixes #1037 
    
<!-- This is an auto-generated description by cubic. -->
---

## Summary by cubic
Enable JSON file support in codebase scanning so common configs and data
(e.g., package.json, vercel.json, translations) are included. Adds .json
to the allowed extensions and removes special-casing for
package.json/vercel.json.

<!-- End of auto-generated description by cubic. -->

e2e-tests/fixtures/import-app/context-manage/manual/baz.json

@@ -1 +1 @@
-["should not be included b/c it's json"]
+["even json is included"]