docs: add extra information about options handling

[rchl]

• Clarify that script setup typechecking does not work
• Clarify that typeCheck options are merged and add info about supported and default values

Fixes #545 Fixes #593

[codecov[bot]]

Codecov Report

Patch and project coverage have no change.

Comparison is base (df0c632) 100.00% compared to head (9bc75da) 100.00%.

:exclamation: Current head 9bc75da differs from pull request most recent head 528a5cb. Consider uploading reports for the commit 528a5cb to get more accurate results

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #594 +/- ## ========================================= Coverage 100.00% 100.00% ========================================= Files 2 2 Lines 36 36 Branches 9 9 ========================================= Hits 36 36 ```

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[rchl]

@danielroe