fix: Validate push notification payload

[mtrezza]

Fixes security vulnerability GHSA-mxhg-rvwx-x993.

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[codecov[bot]]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (346781d) 100.00% compared to head (de99466) 100.00%.

:exclamation: Current head de99466 differs from pull request most recent head b73013b. Consider uploading reports for the commit b73013b to get more accurate results

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #217 +/- ## ========================================= Coverage 100.00% 100.00% ========================================= Files 5 5 Lines 271 277 +6 ========================================= + Hits 271 277 +6 ``` | [Impacted Files](https://app.codecov.io/gh/parse-community/parse-server-push-adapter/pull/217?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=parse-community) | Coverage Δ | | |---|---|---| | [src/APNS.js](https://app.codecov.io/gh/parse-community/parse-server-push-adapter/pull/217?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=parse-community#diff-c3JjL0FQTlMuanM=) | `100.00% <100.00%> (ø)` | | | [src/GCM.js](https://app.codecov.io/gh/parse-community/parse-server-push-adapter/pull/217?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=parse-community#diff-c3JjL0dDTS5qcw==) | `100.00% <100.00%> (ø)` | |

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[parseplatformorg]

🎉 This change has been released in version 4.1.3