Remove escape of + when not followed by whitespace

Closes GH-57.

Author: ocavue

lib/unsafe.js

@@ -88,7 +88,7 @@ export const unsafe = [
   {atBreak: true, character: '*'},
   {character: '*', inConstruct: 'phrasing', notInConstruct: fullPhrasingSpans},
   // A plus sign could start a list item.
-  {atBreak: true, character: '+'},
+  {atBreak: true, character: '+', after: '(?:[ \t\r\n])'},
   // A dash can start thematic breaks, list items, and setext heading
   // underlines.
   {atBreak: true, character: '-'},

test/index.js

@@ -3031,6 +3031,12 @@ test('escape', (t) => {
     'should escape what would otherwise be a character escape'
   )
 
+  t.equal(
+    to({type: 'paragraph', children: [{type: 'text', value: '+a'}]}),
+    '+a\n',
+    'should not escape a `+` if it is not followed by a whitespace'
+  )
+
   t.equal(
     to({
       type: 'paragraph',