Test mitigations for non-Objects

The project currently only covers how objects (i.e. `{ }`) are affected by prototype pollution and what mitigations are available and what they do and don't achieve. For completeness this should be expanded to cover other things as well.

This should also address the [open question currently posed in the `README.md`](https://github.com/ericcornelissen/prototype-pollution-mitigation-tests/blob/1331716c1c28e7714cbbaa3683c5f00dc0fc43b0/README.md?plain=1#L119).

An initial step for this has already been taken in 1331716c1c28e7714cbbaa3683c5f00dc0fc43b0.

## Goals

The goal is to cover at least the following:

- [x] Array (i.e. `[]`) (08fcd059abc85df750600ff24f489f0dabf2b5f3)
- [ ] String (i.e. `""`)
- [ ] numbers (e.g. `42`)
- [ ] booleans (e.g. `true`)