add more test cases

Author: shulaoda

tests/source/issue-6660.rs

@@ -1,4 +1,10 @@
 // rustfmt-wrap_comments: true
 
+// >>text
+// >> text
+// >   >text
+// >   > text
+// ?   ?    text
 // > >= >> >>= >>> >>>=
+// > > = >> >>= >>> >>>=
 fn block_quote() {}

tests/target/issue-6660.rs

@@ -1,4 +1,10 @@
 // rustfmt-wrap_comments: true
 
+// >>text
+// >> text
+// > >text
+// > > text
+// ?   ?    text
 // > >= >> >>= >>> >>>=
+// > > = >> >>= >>> >>>=
 fn block_quote() {}