Fix yiisoft#342: Remove unnecessary files from Composer package

Author: mspirkov

.gitattributes

@@ -1,6 +1,11 @@
 # Ignore all test and documentation for archive
 /.github                    export-ignore
+/tests                      export-ignore
 /.editorconfig              export-ignore
 /.git-blame-ignore-revs     export-ignore
 /.gitattributes             export-ignore
 /.gitignore                 export-ignore
+/phpstan-baseline.neon      export-ignore
+/phpstan.dist.neon          export-ignore
+/phpunit-7x.xml.dist        export-ignore
+/phpunit.xml.dist           export-ignore

CHANGELOG.md

@@ -10,6 +10,7 @@ Yii Framework 2 apidoc extension Change Log
 - Enh #339: Add support for intersection types (mspirkov)
 - Bug #339: Fix the mechanism for replacing `static` with FQCN (mspirkov)
 - Bug #339: Fix processing of multidimensional arrays (mspirkov)
+- Enh #342: Remove unnecessary files from Composer package (mspirkov)
 - Enh #341: Add support for nullable types (mspirkov)