feat: add remote follow

[dodok8]

Summary

Add a remote follow feature.

Related Issue

Closes #10

Changes

• Add Follow button and modal
• Add POST /follow route that redirects to the follow page.
  • Using webfinger, it finds http://ostatus.org/schema/1.0/subscribe rel first, and makes follow links
  • If it doesn't have http://ostatus.org/schema/1.0/subscribe, Use http://webfinger.net/rel/profile-page instead.

Benefits

Users can follow the bot directly on the botkit page.

Checklist

• Did you add a changelog entry to the CHANGES.md?
• Did you write some relevant docs about this change (if it's a new feature)?
• Did you write a regression test to reproduce the bug (if it's a bug fix)?
• Did you write some tests for this change (if it's a new feature)?
• Did you run deno task test-all on your machine?

Additional Notes

I checked it on Misskey(https://yuri.garden), Hacker's Pub(which doesn't implement http://ostatus.org/schema/1.0/subscribe) and Activity Pub Academy.

[gemini-code-assist]

Summary of Changes

Hello @dodok8, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request enhances the bot's web presence by integrating a remote follow mechanism. It provides a user-friendly interface for initiating follows from the bot's page, leveraging Fediverse protocols to redirect users to their respective instance's follow pages, thereby improving cross-instance interaction and the bot's reach within the decentralized network.

Highlights

• Remote Follow Feature: Introduces the ability for users to remotely follow the bot directly from its web interface.
• Follow Button and Modal: Adds a 'Follow' button and an interactive modal dialog to the bot's main page, allowing users to input their Fediverse handle.
• New POST /follow Route: Implements a backend endpoint that handles follow requests. This route uses Webfinger to find the appropriate follow URL, prioritizing 'http://ostatus.org/schema/1.0/subscribe' and falling back to 'http://webfinger.net/rel/profile-page'.

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[gemini-code-assist]

Code Review

This pull request introduces a remote follow feature, which is a valuable addition. My review focuses on improving the implementation for better maintainability, security, and robustness. I've provided suggestions to refactor the client-side scripting in the new FollowButton component, harden the new /follow API endpoint against security vulnerabilities like information leakage, and clean up the code. I also highlighted a potential issue with the fallback logic for constructing follow URLs, which might not be compatible with all Fediverse platforms.

[dahlia]

Could you write a changelog entry too?

[dodok8]

Fedify added template fields in Link in PR fedify-dev/fedify#404.