fix: handle additionalProperties boolean in experimental parser

[mrlubos]

Closes https://github.com/hey-api/openapi-ts/issues/1183

[stackblitz[bot]]

Run & review this pull request in StackBlitz Codeflow.

[changeset-bot[bot]]

🦋 Changeset detected

Latest commit: 7a1a419f07d5ad39e07265771b30d49a4b754a88

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

| Name | Type | | ------------------- | ----- | | @hey-api/openapi-ts | Patch |

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[vercel[bot]]

The latest updates on your projects. Learn more about Vercel for Git ↗︎

Name	Status	Preview	Comments	Updated (UTC)
hey-api-docs	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Nov 6, 2024 7:45am

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 90.32258% with 3 lines in your changes missing coverage. Please review.

Project coverage is 67.83%. Comparing base (23a7484) to head (7a1a419). Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
...ages/openapi-ts/src/openApi/3.0.x/parser/schema.ts	0.00%	3 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #1235 +/- ## ========================================== + Coverage 67.79% 67.83% +0.04% ========================================== Files 132 132 Lines 19342 19349 +7 Branches 1736 1740 +4 ========================================== + Hits 13112 13126 +14 + Misses 6226 6219 -7 Partials 4 4 ``` | [Flag](https://app.codecov.io/gh/hey-api/openapi-ts/pull/1235/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=hey-api) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/hey-api/openapi-ts/pull/1235/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=hey-api) | `67.83% <90.32%> (+0.04%)` | :arrow_up: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=hey-api#carryforward-flags-in-the-pull-request-comment) to find out more.

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.