Add Postgres docs reference

Add the @fedify/botkit-postgres API reference to the VitePress
configuration so the documentation links to its JSR docs alongside the
other BotKit packages.

The change also keeps the markdown language list formatted consistently
with the updated config style.

[ci skip]

Author: dahlia

docs/.vitepress/config.mts

@@ -57,6 +57,10 @@ const references = {
   text: "References",
   items: [
     { text: "@fedify/botkit", link: "https://jsr.io/@fedify/botkit/doc" },
+    {
+      text: "@fedify/botkit-postgres",
+      link: "https://jsr.io/@fedify/botkit-postgres/doc",
+    },
     {
       text: "@fedify/botkit-sqlite",
       link: "https://jsr.io/@fedify/botkit-sqlite/doc",
@@ -168,7 +172,19 @@ export default defineConfig({
   ignoreDeadLinks: true,
 
   markdown: {
-    languages: ["js", "jsx", "ts", "tsx", "typescript", "bash", "sh", "shell", "json", "text", "html"],
+    languages: [
+      "js",
+      "jsx",
+      "ts",
+      "tsx",
+      "typescript",
+      "bash",
+      "sh",
+      "shell",
+      "json",
+      "text",
+      "html",
+    ],
     codeTransformers: [
       transformerTwoslash({
         twoslashOptions: {