Enhancement: Enable `array_indentation` fixer

Closes GH-634.

Include spam_challenge.php only once

The file contains only definitions, and as such multiple inclusion
would never make sense.

Remove silly syntax highlighting work around

This is unlikely to be an issue nowadays.

Enhancement: Enable `single_space_after_construct` fixer

Closes GH-640.

Enhancement: Enable `indentation_type` fixer

Closes GH-622.

Enhancement: Enable `visibility_required` fixer

Closes GH-639.

Enhancement: Enable `whitespace_after_comma_in_array` fixer

Closes GH-637.

Enhancement: Trim trailing whitespace in all files

Closes GH-633.

Enhancement: Enable no_trailing_whitespace fixer

Closes GH-636.

Fix: Remove commented out formats

Closes GH-635.

Enhancement: Run friendsofphp/php-cs-fixer on GitHub Actions

Co-authored-by: Markus Staab <maggus.staab@googlemail.com>

Closes GH-559.

Fix: Remove unused methods

Closes GH-607.

Fix: Remove unused parameters

Closes GH-577.

Enhancement: Add Makefile

Closes GH-621.

Fix: Replace script with tests

Closes GH-631.

Enhancement: Extract constants to avoid mutable global state

Closes GH-626.

Enhancement: Document namespace mapping

Closes GH-625.

Fix: Move and rename tests (#628)

Enhancement: Use autoloader (#614)

Fix: Command (#627)

Fix: Heredoc syntax

Closes GH-564.

Enhancement: Add CONTRIBUTING.md

Co-authored-by: Christoph M. Becker <cmbecker69@gmx.de>

Closes GH-615.

Enhancement: Document platform requirement in composer.json

Closes GH-408.

Changelog: do not confuse GH-xxx with #xxx bugs

Closes GH-619.

drop entry for reverted fix