feat: provide an option to load the remoteEntry.json via a deploy url

[WvKuipersVisma]

This changes allows to provide a deployUrl option when calling initFederation to load the remoteEntry.json file from a custom path or domain like so:

initFederation('/assets/federation.manifest.json', {deployUrl: './custom-root/'})
  .catch(err => console.error(err))
  .then(_ => import('./bootstrap'))
  .catch(err => console.error(err));

or:

initFederation('/assets/federation.manifest.json', {deployUrl: 'http://example.com'})
  .catch(err => console.error(err))
  .then(_ => import('./bootstrap'))
  .catch(err => console.error(err));

This is needed when you run the application on a path other then root or when you want to load the assets over a custom domain. (like an CDN)

Closes #866

[WvKuipersVisma]

@Aukevanoost / @manfredsteyer I Would love to get some feedback (& traction) on this feature as it is a requirement for us to start using native federation.

[Aukevanoost]

Hi @WvKuipersVisma I'll have a look this weekend, thanks for the PR!

[Aukevanoost]

Looks good to me, only one small issue:

initFederation('/assets/federation.manifest.json', {deployUrl: './custom-root/'})
  .catch(err => console.error(err))
  .then(_ => import('./bootstrap'))
  .catch(err => console.error(err));

This doesn't work since you're concatinating the folder URL with a / as well. If you take a look at it I'll merge it!

[Aukevanoost]

As mentioned, can you add an endsWith / check?

[WvKuipersVisma]

@Aukevanoost I implemented the requested change. Should be good to merge

[Aukevanoost]

Fix should be in v21.2.0. I have a small favor. Do you mind also creating this PR on our new v4 repository?
https://github.com/native-federation/native-federation-core/tree/main/packages/runtime