Fix documentation links pointing to non-existent docs.eca.dev

🤖 Generated with [eca](https://eca.dev)

Co-Authored-By: eca <noreply@eca.dev>

Author: ericdallo

website/src/components/Footer.astro

@@ -1,5 +1,5 @@
 ---
-import { REPO_URL, DOCS_URL, SITE_URL } from '../constants';
+import { REPO_URL, SITE_URL } from '../constants';
 ---
 
 <footer class="footer">
@@ -12,7 +12,7 @@ import { REPO_URL, DOCS_URL, SITE_URL } from '../constants';
     </div>
 
     <div class="footer-links">
-      <a href={`${DOCS_URL}/config/plugins/`} target="_blank" rel="noopener">Documentation</a>
+      <a href={`${SITE_URL}/config/plugins/`} target="_blank" rel="noopener">Documentation</a>
       <a href={REPO_URL} target="_blank" rel="noopener">GitHub</a>
       <a href={`${REPO_URL}/blob/master/CONTRIBUTING.md`} target="_blank" rel="noopener">Contribute</a>
       <a href="https://join.slack.com/t/eca-dev/shared_invite/zt-34p6n16s1-_MwEJMr2F~gD2ol4gzntqw" target="_blank" rel="noopener">Community</a>

website/src/components/Header.astro

@@ -1,5 +1,5 @@
 ---
-import { REPO_URL, DOCS_URL, SITE_URL } from '../constants';
+import { REPO_URL, SITE_URL } from '../constants';
 ---
 
 <header class="header">
@@ -14,7 +14,7 @@ import { REPO_URL, DOCS_URL, SITE_URL } from '../constants';
     </a>
 
     <nav class="header-nav">
-      <a href={`${DOCS_URL}/config/plugins/`} class="header-link" target="_blank" rel="noopener">
+      <a href={`${SITE_URL}/config/plugins/`} class="header-link" target="_blank" rel="noopener">
         How plugins work
       </a>
       <a href={REPO_URL} class="header-link" target="_blank" rel="noopener">

website/src/constants.ts

@@ -1,7 +1,6 @@
 // ---- External URLs (single source of truth) ----
 
 export const REPO_URL = 'https://github.com/editor-code-assistant/eca-plugins';
-export const DOCS_URL = 'https://docs.eca.dev';
 export const SITE_URL = 'https://eca.dev';
 
 /** GitHub avatar URL for a given user and pixel size. */