Support for importing XLSX files

6 support importing from xlsx files (#10)

* WIP: XLSX import, affects issue fastbolt/entity-importer#6

* XLSX import working

* Change composer version constraint for fastbolt/test-helpers

* Ignore platform reqs in psalm action

* Add psalm template-implements for ReaderInterface.php

* Add psalm @extends for ReaderInterface.php

* extend symfony extension configuration

* extend symfony extension configuration

* fix unit tests

* Psalm issues

* Psalm issues

* Remove unused use statement

Co-authored-by: Daniel Hirtzbruch <dhh@fastbolt.com>