📖 docs: Add installation guide to README

Author: Abizrh

README.md

@@ -2,5 +2,41 @@
 
 A Neovim plugin for committing with AI
 
-## Usage
+## Installation
 
+### Lazy
+
+```lua
+{
+    'Abizrh/commit-ai.nvim',
+    dependencies = {
+        'nvim-lua/plenary.nvim',
+        'nvim-telescope/telescope.nvim',
+    },
+    config = function()
+        require('commit-ai').setup {
+          icons = false,
+          -- unopiniated commit conventions
+          git_conventions = {
+            docs = { icon = "📖", prefix = "docs", type = "Documentation changes" },
+            fix = { icon = "🐛", prefix = "fix", type = "Bug fix" },
+            feat = { icon = "✨", prefix = "feat", type = "New feature" },
+            enhance = { icon = "⚡", prefix = "enhance", type = "Enhancement" },
+            chore = { icon = "🧹", prefix = "chore", type = "Chore" },
+            refactor = { icon = "⚠️", prefix = "refactor", type = "Breaking change" }
+          },
+          provider_options = {
+            gemini = {
+              model = 'gemini-2.0-flash',
+              api_key = 'YOUR_API_KEY',
+              stream = false,
+            },
+          }
+        }
+    end,
+},
+```
+
+## Contributing
+
+Contributions are welcome! Please feel free to open an issue or submit a pull request.