Added changelog for 0.3.0 (#27)

* Added changelog for 0.3.0

* Typos

CHANGELOG.md

@@ -0,0 +1,22 @@
+# Changelog
+
+All notable changes to this project will be documented in this file, in reverse chronological order by release.
+
+## 0.3.0
+
+### Added
+
+- Return types.
+- Many `InvalidArgumentException`s are thrown when you use invalid arguments. 
+- Integration tests for `UploadedFile` and `ServerRequest`.
+
+### Changed
+
+- We dropped PHP7.0 support. 
+- PSR-17 factories have been marked as internal. They do not fall under our BC promise until PSR-17 is accepted.  
+- `UploadedFileFactory::createUploadedFile` does not accept a string file path. 
+
+## 0.2.3
+
+No changelog before this release
+