Setup CORS headers

[insipx]

CORS headers need to be setup in order to allow WASM requests to go through from the browser. Can try using fetch_mode_no_cors, but the browser itself disallows that request and results in it failing:

ERROR xmtp_mls/src/groups/device_sync.rs:344 sync worker error reqwest error: error sending request inbox_id = "0e773081fe1824c35f9306d414c8c278eed43f57bfe5441119e6a0440d052cee";installation_id = "2054bbe5d616f9aff8ffb9643ac6d9d224711be223f2df408391a8ee97dcef35";

on further investigation this is revealed to be a fetch error:

JsValue(TypeError: Failed to fetchTypeError: Failed to fetch    at http://localhost:8000/wasm-bindgen-test:947:21    at logError (http://localhost:8000/wasm-bindgen-test:17:18)    at imports.wbg.__wbg_fetch_b335d17f45a8b5a1 (http://localhost:8000/wasm-bindgen-test:946:68)    at xmtp_mls-338b2af48685e0b2.wasm.__wbg_fetch_b335d17f45a8b5a1 externref shim (http://localhost:8000/wasm-bindgen-test_bg.wasm:wasm-function[16156]:0x61106d)    at xmtp_mls-338b2af48685e0b2.wasm.reqwest::wasm::client::js_fetch::he87d96ccfb1eabe7 (http://localhost:8000/wasm-bindgen-test_bg.wasm:wasm-function[6332]:0x51a499)    at xmtp_mls-338b2af48685e0b2.wasm.reqwest::wasm::request::RequestBuilder::send::{{closure}}::h3bcd09dd934bfa91 (http://localhost:8000/wasm-bindgen-test_bg.wasm:wasm-function[412]:0x1a062c)    at xmtp_mls-338b2af48685e0b2.wasm.xmtp_mls::groups::device_sync::SyncWorker<ApiClient,V>::on_request::{{closure}}::h36e4e08bd3478bb8 (http://localhost:8000/wasm-bindgen-test_bg.wasm:wasm-function[218]:0x4b3a2)    at xmtp_mls-338b2af48685e0b2.wasm.xmtp_mls::groups::device_sync::SyncWorker<ApiClient,V>::run::{{closure}}::hcf66a7f257dfdc9a (http://localhost:8000/wasm-bindgen-test_bg.wasm:wasm-function[209]:0x210fe)    at xmtp_mls-338b2af48685e0b2.wasm.futures_util::future::future::FutureExt::poll_unpin::h585df9976ee641df (http://localhost:8000/wasm-bindgen-test_bg.wasm:wasm-function[409]:0x19d0a7)    at xmtp_mls-338b2af48685e0b2.wasm.<futures_util::future::select::Select<A,B> as core::future::future::Future>::poll::h911884014f79df2e (http://localhost:8000/wasm-bindgen-test_bg.wasm:wasm-function[8587]:0x57a28a))

fetch_mode_no_cors fundamentally changes the browser response into something different, which reqwest may not expect. Article on topic: https://tpiros.dev/blog/what-is-an-opaque-response/

possibly related: seanmonstar/reqwest#1401