Add release notes for v2.2.0

doc/release-notes-2.2.0.md

@@ -0,0 +1,20 @@
+phpecc 2.2.0
+
+# Performance and Security Enhancements
+
+* Implemented constant-time complete point arithmetic for **secp256k1**
+* Implemented constant-time complete point arithmetic for **NIST P-521**
+* PHP 8.2+: most public API parameters are marked as `SensitiveParameter`
+* PHP 8.1+ with OpenSSL v3+: PHPECC will now prefer OpenSSL if it's available.
+
+To disable OpenSSL for a specific operation, you can call `disableOpenssl()` on the
+`Signer`, `EcDH`, or `NamedCurveFp` classes. To re-enable OpenSSL, the `enableOpenssl()`
+method is provided.
+
+```php 
+$curve = $bobPublicKey->getCurve();
+$curve->disableOpenssl();
+```
+
+**Note**: Due to an issue reported by @mayestik1 in #20 we are no longer specifying a `replace` 
+directive in our composer.json for `mdanter/ecc`,