docs: initial nightly build docs

docs/docs/guides/02-installation/05-nightly-build.md

@@ -0,0 +1,19 @@
+---
+title: Install Nightly Build
+slug: /install/nightly
+description: Jan is a ChatGPT-alternative that runs on your own computer, with a local API server.
+keywords:
+  [
+    Jan AI,
+    Jan,
+    ChatGPT alternative,
+    local AI,
+    private AI,
+    conversational AI,
+    no-subscription fee,
+    large language model,
+    nightly build,
+  ]
+---
+
+https://github.com/janhq/jan?tab=readme-ov-file#download