fix: map axios responseType to correct Response method name

[Minnzen]

Problem

Using responseType: "arraybuffer" throws:

AxiosError: res[(options.responseType || "text")] is not a function

The current code calls res[options.responseType || "text"]() directly on the Fetch API Response object. Axios uses "arraybuffer" (lowercase) but the Fetch API method is arrayBuffer() (camelCase), so res["arraybuffer"] is undefined.

Fix

Map "arraybuffer" to "arrayBuffer" before calling the method on Response.

Test

Added a test case that sends a binary response and requests it with responseType: "arraybuffer". Without the fix it throws the error above; with the fix it returns an ArrayBuffer as expected.