docs(readme): add installation instructions

Author: damienbutt

README.md

@@ -10,6 +10,47 @@ A [NetLinx][netlinx] plugin for [Neovim][neovim].
 -   Syntax highlighting for NetLinx files.
 -   Basic snippets for common NetLinx constructs.
 
+## Installation
+
+Using [lazy.nvim][lazy]:
+
+[lazy]: https://lazy.folke.io/
+
+```lua
+{
+    "Norgate-AV/netlinx.nvim",
+    opts = {},
+}
+```
+
+Using [packer.nvim][packer]:
+
+[packer]: https://github.com/wbthomason/packer.nvim
+
+```lua
+use({
+    "Norgate-AV/netlinx.nvim",
+    config = function()
+        require("netlinx").setup()
+    end,
+})
+```
+
+### Manual Installation
+
+Clone the repository into your Neovim packages directory:
+
+```bash
+git clone https://github.com/Norgate-AV/netlinx.nvim \
+    ~/.local/share/nvim/site/pack/plugins/start/netlinx.nvim
+```
+
+Then add to your `init.lua`:
+
+```lua
+require("netlinx").setup()
+```
+
 ## LICENSE
 
 [MIT](./LICENSE)