Drop old Psalm versions

Adapt array shapes for Psalm 5 (#10)

* Adapt array shapes for psalm5
* Reformat annotations

Psalm 5.x support

v0.3.2

Psalm 5 support (#9)

Psalm 4 fix

v0.3.1

Updated class to conform with Psalm 4's PluginEntryPointInterface. (#6)

Allow use with Psalm 4

v0.3.0

Add Psalm 4 support (#4)

v0.2.1

Add return types for handlers (#3)

Additional stubs

v0.2.0

Added annotation for MockHandler (#1)