all: add support for unordered list with '-'

The unordered list item with hyphen ('-') cause too much confusion and
inconsistency, nevertheless most of still use it.

Case one, given the following markup,

```
- Item 1
+
"A line
of quote"
-- Author
```

Is the "Author" the sub item in list or we are parsing author of quote
paragraph?

Case two, the writer want to write em dash (`—` in HTML Unicode) but
somehow the editor wrap it and start in new line.

As a reminder, the official documentation only recommend using hyphen for
simple list item [1].

[1] https://docs.asciidoctor.org/asciidoc/latest/lists/unordered/#basic-unordered-list

1 files changed, 5 insertions, 5 deletions

diff --git a/testdata/test.adoc b/testdata/test.adoc
index cece8d6..869d720 100644
--- a/testdata/test.adoc
+++ b/testdata/test.adoc
@@ -480,7 +480,7 @@ This line separated by comment.
 ==  Description list
 toc::[]
 
-`CPU`:: The brain
+`AAA`:: The brain
 of
 the
 computer.
@@ -489,23 +489,23 @@ Hard drive:: Permanent storage for operating system and/or user files.
 With `[horizontal]` style,
 
 [horizontal]
-CPU:: The brain of the computer.
+BBB:: The brain of the computer.
 Hard drive:: Permanent storage for operating system and/or user files.
 
 With title,
 
 .A title
-CPU:: The brain of the computer.
+CCC:: The brain of the computer.
 Hard drive:: Permanent storage for operating system and/or user files.
 
 Indented with space
 
-  CPU:: The brain of the computer.
+  DDD:: The brain of the computer.
   Hard drive:: Permanent storage for operating system and/or user files.
 
 With continuation "+",
 
-CPU::
+EEE::
 +
 The brain of the computer.
 Hard drive::