README.md in pact-support-1.20.2 vs README.md in pact-support-1.21.0

@@ -2,5 +2,71 @@
 [![Gem Version](https://badge.fury.io/rb/pact-support.svg)](http://badge.fury.io/rb/pact-support)
 ![Build status](https://github.com/pact-foundation/pact-support/workflows/Test/badge.svg)
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 Provides shared code for the Pact gems
+
+## Compatibility
+
+<details><summary>Specification Compatibility</summary>
+
+| Version  | Stable | [Spec] Compatibility | 
+| -------  | ------ | -------------------- |
+| 1.x.x    | Yes    | 2, 3\*               |
+
+_\*_ v3 support is limited to the subset of functionality required to enable language inter-operable [Message support].
+
+- See V3 tracking [issue](https://github.com/pact-foundation/pact-ruby/issues/318).
+- See V4 tracking [issue](https://github.com/pact-foundation/pact-ruby/issues/319).
+
+Want V3/V4 support now? See the new standalone [pact-verifier](https://github.com/pact-foundation/pact-reference/tree/master/rust/pact_verifier_cli#standalone-pact-verifier)
+
+[message support]: https://github.com/pact-foundation/pact-specification/tree/version-3#introduces-messages-for-services-that-communicate-via-event-streams-and-message-queues
+
+</details>
+
+### Supported matching rules
+
+| matcher       | Spec Version | Implemented | Usage|
+|---------------|--------------|-------------|-------------|
+| Equality      | V1           |   |    |
+| Regex         | V2           | ✅  | `Pact.term(generate, matcher)` |
+| Type          | V2           | ✅  | `Pact.like(generate)` |
+| MinType       | V2           | ✅  | `Pact.each_like(generate, min: <val>)` |
+| MaxType       | V2           |   |    |
+| MinMaxType    | V2           |   |    |
+| Include       | V3           |   |    |
+| Integer       | V3           |   |    |
+| Decimal       | V3           |   |    |
+| Number        | V3           |   |    |
+| Timestamp     | V3           |   |    |
+| Time          | V3           |   |    |
+| Date          | V3           |   |    |
+| Null          | V3           |   |    |
+| Boolean       | V3           |   |    |
+| ContentType   | V3           |   |    |
+| Values        | V3           |   |    |
+| ArrayContains | V4           |   |    |
+| StatusCode    | V4           |   |    |
+| NotEmpty      | V4           |   |    |
+| Semver        | V4           |   |    |
+| EachKey       | V4           |   |    |
+| EachValue     | V4           |   |    |
+
+### Supported generators
+
+Currently limited to provider verification only. No current way to set in consumer tests.
+
+| Generator                | Spec Version | Implemented |
+|------------------------|--------------|----|
+| RandomInt              | V3           | ✅ |
+| RandomDecimal          | V3           | ✅ |
+| RandomHexadecimal      | V3           | ✅ |
+| RandomString           | V3           | ✅ |
+| Regex                  | V3           | ✅ |
+| Uuid                   | V3/V4        | ✅ |
+| Date                   | V3           | ✅ |
+| Time                   | V3           | ✅ |
+| DateTime               | V3           | ✅ |
+| RandomBoolean          | V3           | ✅ |
+| ProviderState          | V4           | ✅ |
+| MockServerURL          | V4           | 🚧 |