Add special goto def/docs support in doom! blocks

- Pressing gd on a module in your doom! block will now browse that
  module's directory.
- Pressing K on a module will jump to that module's documentation, if any.
- Pressing K on a module flag will jump to that flag's description
  within that module's documenation.
- This is now explained in init.example.el

Closes #2249

modules/editor/file-templates/templates/org-mode/__doom-readme

@@ -8,7 +8,7 @@
                   "")`}
 #+DATE:    `(format (format-time-string "%B %%s, %Y") (string-to-number (format-time-string "%d")))`
 #+SINCE:   ${2:{replace with next tagged release version}}
-#+STARTUP: inlineimages
+#+STARTUP: inlineimages nofold
 
 * Table of Contents :TOC_3:noexport: