Add missing union overloads to FormData type definitions

[edmundhung]

Fixes #5934

Updated FormData types based on https://github.com/microsoft/TypeScript/blob/d9d9eeafa0a2bb1fd327b3af15edacade7544e5f/src/lib/dom.generated.d.ts#L12573-L12615

[github-actions]

The generated output of @cloudflare/workers-types has been changed by this PR. If this is intentional, run just generate-types to update the snapshot. Alternatively, you can download the full generated types:

Full Type Diff

diff -r types/generated-snapshot/latest/index.d.ts bazel-bin/types/definitions/latest/index.d.ts
1650a1651,1656
>   append(name: string, value: string | Blob): void;
>   /**
>    * The **`append()`** method of the FormData interface appends a new value onto an existing key inside a `FormData` object, or adds the key if it does not already exist.
>    *
>    * [MDN Reference](https://developer.mozilla.org/docs/Web/API/FormData/append)
>    */
1681a1688,1693
>   /**
>    * The **`set()`** method of the FormData interface sets a new value for an existing key inside a `FormData` object, or adds the key/value if it does not already exist.
>    *
>    * [MDN Reference](https://developer.mozilla.org/docs/Web/API/FormData/set)
>    */
>   set(name: string, value: string | Blob): void;
diff -r types/generated-snapshot/latest/index.ts bazel-bin/types/definitions/latest/index.ts
1655a1656,1661
>   append(name: string, value: string | Blob): void;
>   /**
>    * The **`append()`** method of the FormData interface appends a new value onto an existing key inside a `FormData` object, or adds the key if it does not already exist.
>    *
>    * [MDN Reference](https://developer.mozilla.org/docs/Web/API/FormData/append)
>    */
1686a1693,1698
>   /**
>    * The **`set()`** method of the FormData interface sets a new value for an existing key inside a `FormData` object, or adds the key/value if it does not already exist.
>    *
>    * [MDN Reference](https://developer.mozilla.org/docs/Web/API/FormData/set)
>    */
>   set(name: string, value: string | Blob): void;

[codspeed-hq]

CodSpeed Performance Report

Merging this PR will degrade performance by 11.51%

_{Comparing edmundhung/fix-formdata-union-overloads (bf83ba3) with main (2752663)}

Summary

❌ 2 regressed benchmarks
✅ 68 untouched benchmarks
⏩ 129 skipped benchmarks¹

⚠️ Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Benchmark	BASE	HEAD	Efficiency
❌	simpleStringBody[Response]	19.1 µs	21.6 µs	-11.48%
❌	Encode_ASCII_32[TextEncoder][0/0/32]	3 ms	3.4 ms	-11.51%

Footnotes

1. 129 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩