Use headings for credits

Author: dinomite

release-notes/CREDITS-2.x

@@ -13,128 +13,117 @@ Authors:
 
 Contributors:
 
+# 2.13.NEXT
+
 Stefan Schmid (schmist@github)
 * #519: Contributed test for #518 (null should deserialize to _the_ Unit instance)
 
 wrongwrong (k163377@github)
 * #456: Refactor KNAI.findImplicitPropertyName()
 * #449: Refactor AnnotatedMethod.hasRequiredMarker()
-  (2.13.NEXT)
 
 Dmitri Domanine (novtor@github)
 * Contributed fix for #490: Missing value of type JsonNode? is deserialized as NullNode instead of null
-  (2.13.NEXT)
+
+# 2.13.0
 
 Fedor Bobin (Fuud@github)
 * #496, #45: Fix treeToValue extension function should not have type erasure
-  (2.13)
 
 Mikhael Sokolov (sokomishalov@github)
 * #489: JsonNode, ArrayNode and ObjectNode extension functions
-  (2.13)
 
 Max Wiechmann (MaxMello@github)
 * #494: ProGuard ProTips in the README
-  (2.13)
 
 Róbert Papp (TWiStErRob@github)
 * #477: KotlinFeature documentation & deprecation replacements
-  (2.13)
 
 wrongwrong (k163377@github)
 * #468: Improved support for value classes
-  (2.13)
 
 wrongwrong (k163377@github)
 * #460: Test for GitHub #451 (`-` in property name handling)
-  (2.13)
 
 wrongwrong (k163377@github)
 * #447: Fix edge case when dealing with sealed classes
-  (2.13)
 
 wrongwrong (k163377@github)
 * Contributed #438: Fixed mapping failure when `private` `companion object` is named
-  (2.13)
+
+# 2.12.5
 
 Marshall Pierce (marshallpierce@github)
 * #474: Reported disrespect for @JsonProperty on parent class
-  (2.12.5)
 
 Christopher Mason (masoncj@github)
 * #194: Contributed test case for @JsonIdentityInfo usage
-  (2.12.5)
 
 Martin Häusler (MartinHaeusler@github)
 * Reported #194: @JsonIdentityInfo bug
-  (2.12.5)
+
+# 2.12.2
 
 Eric Fenderbosch (efenderbosch@github)
 * Fixed #182: Serialize unsigned numbers
-  (2.12.2)
 
 Elisha Peterson (triathematician@github)
 * Reported #409: `module-info.java` missing "exports"
-  (2.12.2)
+
+# 2.12.1
 
 Wolfgang Jung (elektro-wolle@github)
 * Fixed inline class serialization
-  (2.12.1)
+
+# 2.12.0
 
 John Flynn (Neuman968@github)
 * Contributed extension methods for SimpleModule to add serializer and deserializer
   extension functions for KClass #322
-  (2.12.0)
 
 Mateusz Stefek (MateuszStefek@github)
 * Reported #321: Make MissingKotlinParameterException a descendant of MismatchedInputException
-  (2.12.0)
 
 Hideaki Tanabe (tanabe@github)
 * Brought README.md into the modern world of Gradle (compile -> implementation)
-  (2.12.0)
 
 Hidde Wieringa (hiddewie@github)
 * Contributed test case for issue 308
 * Contributed Kotlin DSL constructor
- (2.12.0)
 
 David Riggleman (DavidRigglemanININ@github)
 * Wrote strict null checking for collection values
- (2.12.0)
+
+# 2.11.0
 
 Drew Stephens (dinomite@github)
 * Contributed fix for #281: KotlinObjectSingletonDeserializer fails to deserialize
   previously serialized JSON as it doesn't delegate deserializeWithType
- (2.11.0)
+
+# 2.10.2
 
 Patrick Strawderman (kilink@github)
 * Reported #279: 2.10 introduces another binary compatibility issue in `KotlinModule`
   constructor
- (2.10.2)
 
 Vladimir Petrakovich (frost13it@github)
 * Contributed fix for #279: 2.10 introduces another binary compatibility issue in
   `KotlinModule` constructor
- (2.10.2)
+
+# 2.10.1
 
 Stéphane B (StephaneBg@github)
 * Submitted fix for #176: Version 2.9.7 breaks compatibility with Android minSdk < 24
- (2.10.1)
 
 Alain Lehmann (ciderale@github)
 * Contributed fix for #225: Don't instantiate new instances of Kotlin singleton objects
- (2.10.1)
 
 Andrey Lipatov (LipatovAndrey@github)
 * Contributed fix for #80: Boolean property name starting with 'is' not serialized /
   deserialized properly
- (2.10.1)
 
 Konstantin Volivach (kostya05983@github)
 * Contributed fix for #254: Add serializers for Sequences
- (2.10.1)
 
 Laimonas Turauskas (Laimiux@github)
 * Contributed fix for #180: handle nullable method parameters correctly (for creator methods)
- (2.10.1)