[new] Support literate Djot files

Djot is a markup format that is derived from CommonMark, it's code block
syntax is identical to CommonMark's, so we can support it as a
CommonMark style literate formate by just adding the file extension.

CHANGELOG_NEXT.md

@@ -122,6 +122,9 @@ This CHANGELOG describes the merged but unreleased changes. Please see [CHANGELO
   with `_builtin.<TAG>` (eg `_builtin.CONS`). This allows the identity optimisation
   to optimise conversions between list-shaped things.
 
+* [Djot](https://djot.net/) files can now be compiled as CommonMark style
+  Literate Idris files.
+
 ### Backend changes
 
 #### RefC Backend

CONTRIBUTORS

@@ -56,6 +56,7 @@ Michael Morgan
 Milan Kral
 Molly Miller
 Mounir Boudia
+Nathan McCarty
 Nick Drozd
 Nicolas Biri
 Niklas Larsson

docs/source/reference/literate.rst

@@ -86,7 +86,7 @@ Each of the following markup is recognised regardless of case:
 CommonMark
 **********
 
-We treat files with an extension of ``.md`` and ``.markdown`` as CommonMark style literate files.
+We treat Markdown files with an extension of ``.md`` or ``.markdown`` and Djot files with an extension of ``.dj`` as CommonMark style literate files.
 
 + CommonMark source blocks for idris sans options are recognised as visible code blocks::
 

src/Parser/Unlit.idr

@@ -33,7 +33,7 @@ styleCMark : LiterateStyle
 styleCMark = MkLitStyle
               [("```idris", "```"), ("~~~idris", "~~~"), ("<!-- idris", "-->")]
               Nil
-              [".md", ".markdown"]
+              [".md", ".markdown", ".dj"]
 
 export
 styleTeX : LiterateStyle