fix: handle non-printable characters in browser responses

[achingbrain]

Fixes a regression introduced by #54 - in the browser by default the response body is interpreted as a string which can become corrupted when non-printable characters are encountered.

Setting the responseType param to arraybuffer makes it behave in a similar way to node.

This is currently manifesting itself as a browser test failure for ipfs as the DAG node is retrieved from the server with garbage characters in the block:

ipfs-http-client: FAILED TESTS:
ipfs-http-client:   .dag
ipfs-http-client:     ✖ should be able to put and get a DAG node with format dag-cbor
ipfs-http-client:       Chrome Headless 84.0.4147.125 (Linux x86_64)
ipfs-http-client:     Error: Undeterminated nesting
ipfs-http-client:         at Decoder._decode (file:/home/travis/build/ipfs/js-ipfs/node_modules/borc/src/decoder.js:603:15)
ipfs-http-client:         at Decoder.decodeAll (file:/home/travis/build/ipfs/js-ipfs/node_modules/borc/src/decoder.js:624:10)
ipfs-http-client:         at Object.exports.deserialize (file:/home/travis/build/ipfs/js-ipfs/node_modules/ipld-dag-cbor/src/util.js:169:23)
ipfs-http-client:         at Object.exports.resolve (file:/home/travis/build/ipfs/js-ipfs/node_modules/ipld-dag-cbor/src/resolver.js:27:19)
ipfs-http-client:         at Object.eval [as get] (file:/home/travis/build/ipfs/js-ipfs/packages/ipfs-http-client/src/dag/get.js:36:24)
ipfs-http-client:         at async Context.eval (file:/home/travis/build/ipfs/js-ipfs/packages/ipfs-http-client/test/dag.spec.js:58:20)

[achingbrain]

This is a band-aid, see #54 (comment)

[jacobheun]

This is a band-aid, see #54 (comment)

We should just close this and revert the change until we can do progress updates properly then

[jacobheun]

We've decided not to do this.