add doctor for shell and update readme

modules/lang/sh/README.org

@@ -9,14 +9,18 @@ This module adds support for shell scripting languages.
 
 * Table of Contents :TOC:
 - [[#install][Install]]
+  - [[#dependencies][Dependencies]]
 - [[#appendix][Appendix]]
   - [[#commands][Commands]]
 
 * Install
-This module has no dependencies.
+** Dependencies
+This module has one soft dependency:
+
++ ~shellcheck~ Enables shell script linting.
 
 * Appendix
 ** Commands
-| command    | key / ex command | description                                           |
+| command         | key / ex command | description                                           |
-|------------+------------------+-------------------------------------------------------|
+|-----------------+------------------+-------------------------------------------------------|
-| ~+sh/repl~ | =:repl=          | Open a terminal (or send the current selection to it) |
+| ~+sh/open-repl~ | =:repl=          | Open a terminal (or send the current selection to it) |

modules/lang/sh/doctor.el

@@ -0,0 +1,5 @@
+;;; lang/sh/doctor.el -*- lexical-binding: t; -*-
+
+(when! (not (executable-find "shellcheck"))
+  (warn! "Couldn't find shellcheck. Shell script linting will not work"))
+