Move lsp config to local file structure

.config/nvim/lsp/cairo_ls.lua

@@ -0,0 +1,20 @@
+---@brief
+---
+--- [Cairo Language Server](https://github.com/starkware-libs/cairo/tree/main/crates/cairo-lang-language-server)
+---
+--- First, install Cairo following [this tutorial](https://book.cairo-lang.org/ch01-01-installation.html)
+---
+--- Then enable Cairo Language Server in your Lua configuration.
+--- ```lua
+--- vim.lsp.enable('cairo_ls')
+--- ```
+---
+--- *cairo-language-server is still under active development, some features might not work yet !*
+
+---@type vim.lsp.Config
+return {
+  init_options = { hostInfo = 'neovim' },
+  cmd = { 'scarb', 'cairo-language-server', '/C', '--node-ipc' },
+  filetypes = { 'cairo' },
+  root_markers = { 'Scarb.toml', 'cairo_project.toml', '.git' },
+}