also use gfm header generation in test and debug configuraitons

Signed-off-by: hoijui <[email protected]>

Author: hoijui

config.json.example

@@ -3,7 +3,8 @@
         "db": {
             "dialect": "sqlite",
             "storage": ":memory:"
-        }
+        },
+        "linkifyHeaderStyle": "gfm"
     },
     "development": {
         "loglevel": "debug",
@@ -13,7 +14,8 @@
         "db": {
             "dialect": "sqlite",
             "storage": "./db.codimd.sqlite"
-        }
+        },
+        "linkifyHeaderStyle": "gfm"
     },
     "production": {
         "domain": "localhost",