Add Elixir support and config

lua/lazyvim/plugins/extras/lang/elixir.lua

@@ -0,0 +1,32 @@
+return {
+  {
+    "nvim-treesitter/nvim-treesitter",
+    opts = function(_, opts)
+      vim.list_extend(opts.ensure_installed, {
+        "elixir",
+        "heex",
+        "eex",
+      })
+    end,
+  },
+  {
+    "williamboman/mason.nvim",
+    opts = function(_, opts)
+      vim.list_extend(opts.ensure_installed, {
+        "elixir-ls",
+      })
+    end,
+  },
+  {
+    "nvim-neotest/neotest",
+    optional = true,
+    dependencies = {
+      "jfpedroza/neotest-elixir",
+    },
+    opts = {
+      adapters = {
+        ["neotest-elixir"] = {},
+      },
+    },
+  },
+}