Bump tinacms from 1.5.6 to 1.5.20

Bumps [tinacms](https://github.com/tinacms/tinacms/tree/HEAD/packages/tinacms) from 1.5.6 to 1.5.20.
- [Release notes](https://github.com/tinacms/tinacms/releases)
- [Changelog](https://github.com/tinacms/tinacms/blob/main/packages/tinacms/CHANGELOG.md)
- [Commits](https://github.com/tinacms/tinacms/commits/tinacms@1.5.20/packages/tinacms)

---
updated-dependencies:
- dependency-name: tinacms
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

package.json

@@ -34,7 +34,7 @@
     "react-icons": "^4.2.0",
     "styled-jsx": "^3.2.5",
     "tailwindcss": "^3.2.4",
-    "tinacms": "^1.5.6",
+    "tinacms": "^1.5.20",
     "typescript": "^4.5.2"
   }
 }