Add emacs lsp-mode documentation and fix typo (#47)

README.md

@@ -107,6 +107,31 @@ if executable('nil')
 endif
 ```
 
+### Emacs with [`lsp-mode`]
+
+[`lsp-mode`]: https://github.com/emacs-lsp/lsp-mode
+
+Add the following elisp code to your configuration. (using `use-package`)
+
+```elisp
+(use-package lsp-mode
+  :ensure t)
+
+(use-package lsp-nix
+  :ensure lsp-mode
+  :after (lsp-mode)
+  :demand t
+  :custom
+  (lsp-nix-nil-formatter ["nixpkgs-fmt"]))
+
+(use-package nix-mode
+  :hook (nix-mode . lsp-deferred)
+  :ensure t)
+```
+
+There are various other configurations to tweak it. Refer the
+[specific manual page](https://emacs-lsp.github.io/lsp-mode/page/lsp-nix-nil/ "https://emacs-lsp.github.io/lsp-mode/page/lsp-nix-nil/") for more details.
+
 ### Emacs with [`eglot`]
 
 [`eglot`]: https://github.com/joaotavora/eglot

docs/configuration.md

@@ -1,7 +1,7 @@
 ## LSP Configuration
 
 There are some tunable options and settings for `nil`.
-They are retrieved via LSP and support runtine modification.
+They are retrieved via LSP and support runtime modification.
 
 All settings are nested under a key `"nil"`.
 For example, `formatting.command` means to write
@@ -24,7 +24,7 @@ The values shown here are the default values.
       // It should accepts file content in stdin and print the formatted code into stdout.
       // Type: [string] | null
       // Example: ["nixpkgs-fmt"]
-      "command": null, 
+      "command": null,
     },
     "diagnostics": {
       // Ignored diagnostic kinds.