Add `server` middlewares defined in packages to the Koa app

[DAreRodz]

What:

Get middlewares exposed by Frontity packages in the server property and register them into the Koa server.

Co-authored-by: @cristianbote

Why:

To close #696

Tasks:

• [ ] Code
• [ ] TSDocs
• [ ] TypeScript
• [ ] Unit tests
• [ ] End to end tests
• [ ] TypeScript tests
• [ ] Update community discussions
• [ ] Add a changeset (with link to its Feature Discussion if it exists)

Unrelated Tasks

• [ ] Update starter themes
• [ ] Update other packages

[changeset-bot[bot]]

⚠️ No Changeset found

Latest commit: 409fe416730c834b60293c40bbc86fc718558734

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

This PR includes no changesets

When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types

Click here to learn what changesets are, and how to add one.

Click here if you're a maintainer who wants to add a changeset to this PR

[github-actions[bot]]

ESLint Summary View Full Report

Annotations are provided inline on the Files Changed tab. You can also see all annotations that were generated on the annotations page.

Type	Occurrences	Fixable
Errors	0	0
Warnings	0	0
Ignored	0	N/A

• Result: :white_check_mark: success
• Annotations: 0 total

---

^{Report generated by eslint-plus-action}

[DAreRodz]

After doing some minimal testing, I've noticed that middlewares are registered for each request, again and again. That would be fixed though once we implement https://github.com/frontity/frontity/issues/695.

@SantosGuillamot should I mark the issue as blocked?

[SantosGuillamot]

Sure, I have just done it :slightly_smiling_face: