Fix homepage feature links (404s and wrong URL)

[alienx5499]

Summary

Fixes broken behavior for the homepage feature buttons (API docs, Go, JS):

1. 404 on API docs — The "API docs" link pointed to /developer/http-api, which does not exist on drand.love; developer docs live on docs.drand.love. The correct URL is https://docs.drand.love/dev-guide/developer/http-api.

2. Wrong URL when clicking — Using <router-link :to="..."> with full https:// URLs made Vue Router treat them as paths, so clicks opened e.g. http://localhost:8082/https:/docs.drand.love/... instead of the real docs URL. External links now use a plain <a> so they open correctly.

What's wrong on live (https://drand.love/)

• API docs → Points to https://drand.love/developer/http-api. That path doesn't host the real API docs (they're on docs.drand.love), so users get the wrong page or a 404.
• Go / JS → Rendered as drand.love/https:/docs.drand.love/developer/clients/#go- (and same for JS). The site origin is prepended to the full URL, so the link is invalid and breaks in production as well as on localhost.

Screenshots

Before (live site)

API docs — docs.drand.love Page Not Found	Go — drand.love 404	JS — drand.love 404

Changes

1. docs/README.md

   • API docs button: link: /developer/http-api → link: https://docs.drand.love/dev-guide/developer/http-api
   • Go and JS links unchanged (already valid: .../developer/clients/#go- and #javascript--typescript-).

2. docs/.vuepress/theme/components/Home.vue

   • Feature action links that start with http:// or https:// now render as <a href="..." target="_blank" rel="noopener noreferrer"> instead of <router-link :to="...">, so external URLs open in a new tab and no longer get the current origin prepended (fixes the malformed URL in both dev and production).
   • Links that do not start with http:// or https:// (e.g. /about/, /loe/) still use <router-link> and behave as before. Only the three feature buttons are affected; the rest of the page (Learn more, Get involved, footer, nav, etc.) is unchanged and still uses VuePress's default link handling.

Checklist

• API docs link points to valid docs.drand.love page
• Go / JS links unchanged and valid
• External links open in new tab and no longer get origin prepended
• Relative links and rest of page (Learn more, Get involved, footer, nav) unchanged
• Screenshot added above (before, from live site)

[alienx5499]

@AnomalRoil @CluEleSsUK This PR fixes two production issues on drand.love:

1. The homepage “API docs” button pointed to a non-existent path — it now links to the correct docs.drand.love HTTP API page.
2. External links (Go & JS buttons) were using router-link, which caused incorrect URLs like drand.love/https:/docs.drand.love/.... These now use a standard <a target="_blank"> and open correctly.

Marking for visibility since this affects live users.