feat: support proxy options for http client

[enix223]

What kind of change does this PR introduce?

• [ ] Bugfix
• [x] Feature
• [ ] Docs
• [ ] New Binding issue #___
• [ ] Code style update
• [ ] Refactor
• [ ] Build-related changes
• [ ] Other, please describe:

Does this PR introduce a breaking change?

• [ ] Yes, and the changes were approved in issue #___
• [x] No

Checklist

• [ ] When resolving issues, they are referenced in the PR's title (e.g fix: remove a typo, closes #___, #___)
• [x] A change file is added if any packages will require a version bump due to this PR per the instructions in the readme.
• [ ] I have added a convincing reason for adding this feature, if necessary

Other information

This PR enhances the http api to support setting http proxy when building a client.

Usage:

import { getClient } from '@tauri-apps/api/http';

// simple form
let client = await getClient({
  proxyUrl: 'http://localhost:1234',
});

// basic authentication form
let client = await getClient({
  proxyUrl: 'http://localhost:1234',
  proxyUser: 'foo',
  proxyPassword: 'bar'
});

// no proxy form
let client = await getClient({
  proxyUrl: 'http://localhost:1234',
  noProxy: 'www.example.com',
});

These proxy options are supported for both reqwest-client and attohttpc features.