Add remote_asset_loader example

[afonsolage]

Objective

• Showcase how to use AssetReader and AssetWriter to download an asset from a CDN when it doesn't exists local.

Solution

• Add an example (remote_asset_loader) which showcases how to download an asset from a CDN.
• Add ehttp as a new dev-dependencies.

Additional Context

• This is somewhat related to #11694 since I'm also using ehttp and the same features.
• This example won't work on wasm or Android since I need AssetWriter.
• I'm using a Google Font since its Open Font License and it is compatible with MIT and Apache 2.0 (AFAIK);
• At the end of the example main, I use std::fs::remove_file to "manually" do some cleanup, to avoid adding things to asset folder whenever someone runs this example.

[github-actions[bot]]

The generated examples/README.md is out of sync with the example metadata in Cargo.toml or the example readme template. Please run cargo run -p build-templated-pages -- update examples to update it, and commit the file change.