docs: add installation

Author: imrim12

content/1.docs/1.getting-started/2.installation.md

@@ -0,0 +1,21 @@
+---
+title: Installation
+description: Get started with Nuxt UI Pro SaaS template.
+---
+
+## Quick Start
+
+You can start a fresh new project with:
+
+```bash [Terminal]
+npx nuxi init -t github:nuxt-ui-pro/saas
+```
+
+or create a new repository from GitHub:
+
+1. Open <https://github.com/nuxt-ui-pro/saas>
+2. Click on `Use this template` button
+3. Enter repository name and click on `Create repository from template` button
+4. Clone your new repository
+5. Install dependencies with your favorite package manager
+6. Start development server