feat: add elixir stuff

modules/programs/nvim/plugins/lua/conform.lua

@@ -2,6 +2,7 @@ local conform = require("conform")
 
 local formatters_by_ft = {
   ["*"] = { "codespell", "trim_whitespace" },
+  elixir = { "mix" },
   gleam = { "gleam" },
   go = { "gofmt" },
   json = { "jq" },

modules/programs/nvim/plugins/lua/nvim-lspconfig.lua

@@ -133,6 +133,10 @@ for _, lsp in ipairs(servers) do
   lspconfig_setup(lsp, {})
 end
 
+lspconfig_setup("elixirls", {
+  cmd = { "elixir-ls" },
+})
+
 lspconfig_setup("nixd", {
   settings = {
     nixd = {