Set rel nofollow to external links

yarn.lock

@@ -950,6 +950,13 @@ __metadata:
   languageName: node
   linkType: hard
 
+"@ungap/structured-clone@npm:^1.0.0":
+  version: 1.3.0
+  resolution: "@ungap/structured-clone@npm:1.3.0"
+  checksum: 10c0/0fc3097c2540ada1fc340ee56d58d96b5b536a2a0dab6e3ec17d4bfc8c4c86db345f61a375a8185f9da96f01c69678f836a2b57eeaa9e4b8eeafd26428e57b0a
+  languageName: node
+  linkType: hard
+
 "abbrev@npm:^2.0.0":
   version: 2.0.0
   resolution: "abbrev@npm:2.0.0"
@@ -2020,6 +2027,13 @@ __metadata:
   languageName: node
   linkType: hard
 
+"is-absolute-url@npm:^4.0.0":
+  version: 4.0.1
+  resolution: "is-absolute-url@npm:4.0.1"
+  checksum: 10c0/6f8f603945bd9f2c6031758bbc12352fc647bd5d807cad10d96cc6300fd0e15240cc091521a61db767e4ec0bacff257b4f1015fd5249c147bbb4a4497356c72e
+  languageName: node
+  linkType: hard
+
 "is-arrayish@npm:^0.3.1":
   version: 0.3.2
   resolution: "is-arrayish@npm:0.3.2"
@@ -2771,6 +2785,20 @@ __metadata:
   languageName: node
   linkType: hard
 
+"rehype-external-links@npm:3.0.0":
+  version: 3.0.0
+  resolution: "rehype-external-links@npm:3.0.0"
+  dependencies:
+    "@types/hast": "npm:^3.0.0"
+    "@ungap/structured-clone": "npm:^1.0.0"
+    hast-util-is-element: "npm:^3.0.0"
+    is-absolute-url: "npm:^4.0.0"
+    space-separated-tokens: "npm:^2.0.0"
+    unist-util-visit: "npm:^5.0.0"
+  checksum: 10c0/486b5db73d8fe72611d62b4eb0b56ec71025ea32bba764ad54473f714ca627be75e057ac29243763f85a77c3810f31727ce3e03c975b3803c1c98643d038e9ae
+  languageName: node
+  linkType: hard
+
 "rehype-katex-svelte@npm:1.2.0":
   version: 1.2.0
   resolution: "rehype-katex-svelte@npm:1.2.0"
@@ -3771,6 +3799,7 @@ __metadata:
     mdsvex: "npm:0.12.3"
     misskey-js: "npm:2024.11.1-alpha.0"
     prismjs: "npm:1.29.0"
+    rehype-external-links: "npm:3.0.0"
     rehype-katex: "npm:7.0.1"
     rehype-katex-svelte: "npm:1.2.0"
     remark-footnotes: "npm:2.0"