Problem Matcher: Capture code and severity

Make the problem matcher capture Hadolint's output more acurately.

related-to: hadolint/hadolint-action#78

Signed-off-by: Moritz Röhrich <moritz@ildefons.de>

problem-matcher.json

@@ -4,10 +4,12 @@
       "owner": "hadolint/hadolint-action",
       "pattern": [
         {
-          "regexp": "(.*)\\:(\\d+)\\s(.*)",
+          "regexp": "^(.+):(\\d+)\\s(.+)\\s(error|warning|info|style):\\s(.+)$",
           "file": 1,
           "line": 2,
-          "message": 3
+          "code": 3,
+          "severity": 4,
+          "message": 5
         }
       ]
     }