Add Publishing Secrets page with pgp key generator

Author: armanbilge

docs/directory.conf

@@ -1,6 +1,7 @@
 laika.navigationOrder = [
   index.md
   site.md
+  secrets.md
   faq.md
   customization.md
-]
+]

docs/secrets.md

@@ -0,0 +1,39 @@
+# Publishing Secrets
+
+## Generate a PGP key
+
+Key generation occurs locally in your browser using [OpenPGP.js](https://github.com/openpgpjs/openpgpjs).
+
+<div>
+  <script src="https://cdn.jsdelivr.net/npm/[email protected]/dist/openpgp.min.js"></script>
+  <script type="text/javascript">
+    async function tlGenerateKey() {
+      const project = document.getElementById('project').value
+      const email = document.getElementById('email').value
+      const { publicKey, privateKey } = await openpgp.generateKey({
+        userIDs: [{ name: `${project} bot`, email }]
+      });
+      document.getElementById('publicKey').value = publicKey;
+      document.getElementById('privateKey').value = btoa(privateKey);
+    }
+  </script>
+
+  <label for="project"><b>Your project name:</b></label><br/>
+  <input type="text" id="project" name="project" size="64"/><br/>
+  <label for="email"><b>Your email:</b></label><br/>
+  <input type="text" id="email" name="email" size="64"/><br/>
+  <button onClick="tlGenerateKey()">Generate Key</button>
+
+</div>
+
+### Public key
+
+Copy-paste and submit your public key to the [Ubuntu key server](https://keyserver.ubuntu.com/).
+
+<textarea id="publicKey" readonly rows="16" cols="64" style="resize: none;"></textarea>
+
+### Private key
+
+Copy-paste and set your private key as the `PGP_SECRET` in your repository secrets.
+
+<textarea id="privateKey" readonly rows="16" cols="64" style="resize: none;"></textarea>