lexers/cue: support definitions and dollars in field names

'$' is valid in a bare field name in CUE. It is not special. It happens
to be used by convention at the start of field names, but that is about
it.

Definitions start with '#'.

Add a "section" of tests that cover the various types of field. There
are no errors in new "tests", whereas before (i.e. without the change to
the CUE lexer) there would have been.

lexers/embedded/cue.xml

@@ -49,7 +49,7 @@
       <rule pattern="(true|false|null|_)\b">
         <token type="KeywordConstant"/>
       </rule>
-      <rule pattern="[_a-zA-Z]\w*">
+      <rule pattern="#?[_a-zA-Z$]\w*">
         <token type="Name"/>
       </rule>
     </state>

lexers/testdata/cue.actual

@@ -29,3 +29,8 @@ A: close({
     field2: string
 })
 
+// Verify that various field types work
+_hidden: int
+regular: int
+$id: int
+#definition: int

lexers/testdata/cue.expected

@@ -104,5 +104,27 @@
   {"type":"KeywordType","value":"string"},
   {"type":"Text","value":"\n"},
   {"type":"Punctuation","value":"})"},
-  {"type":"Text","value":"\n\n"}
+  {"type":"Text","value":"\n\n"},
+  {"type":"CommentSingle","value":"// Verify that various field types work"},
+  {"type":"Text","value":"\n"},
+  {"type":"Name","value":"_hidden"},
+  {"type":"Operator","value":":"},
+  {"type":"Text","value":" "},
+  {"type":"KeywordType","value":"int"},
+  {"type":"Text","value":"\n"},
+  {"type":"Name","value":"regular"},
+  {"type":"Operator","value":":"},
+  {"type":"Text","value":" "},
+  {"type":"KeywordType","value":"int"},
+  {"type":"Text","value":"\n"},
+  {"type":"Name","value":"$id"},
+  {"type":"Operator","value":":"},
+  {"type":"Text","value":" "},
+  {"type":"KeywordType","value":"int"},
+  {"type":"Text","value":"\n"},
+  {"type":"Name","value":"#definition"},
+  {"type":"Operator","value":":"},
+  {"type":"Text","value":" "},
+  {"type":"KeywordType","value":"int"},
+  {"type":"Text","value":"\n"}
 ]