Add test for regexes inb out section.

Author: brunns

README.md

@@ -130,12 +130,13 @@ Implementation notes:
 #### 4. Regular expressions in expectations
 
 ```yaml
-- case: with_out
+- case: expected_message_regex_with_out
   regex: yes
   main: |
-    reveal_type('abc')
+    a = 'abc'
+    reveal_type(a)
   out: |
-    main:1: note: .*str.*
+    main:2: note: .*str.*
 ```
 
 ## Options

pytest_mypy_plugins/tests/test-regex_assertions.yml

@@ -6,3 +6,11 @@
 
     reveal_type(a)  # N: Revealed type is "builtins.int"
     reveal_type(b)  # N: .*str.*
+
+- case: expected_message_regex_with_out
+  regex: yes
+  main: |
+    a = 'abc'
+    reveal_type(a)
+  out: |
+    main:2: note: .*str.*