Add a pull request template which contains helpful information #520

Job	Run time
PHPUnit (PHP 7.1)	28s
PHPUnit (PHP 7.2)	20s
PHPUnit (PHP 7.3)	22s
PHPUnit (PHP 7.4)	54s
PHPUnit (PHP 8.0)	27s
PHPUnit (PHP 8.1)	18s
PHPUnit (PHP 8.2)	26s
PHPUnit (PHP 8.3)	49s
PHPUnit Composer v2 (PHP 7.4)	24s
Tests alternative autoloader (PHP 7.1)	12s
Tests alternative autoloader (PHP 7.2)	8s
Tests alternative autoloader (PHP 7.3)	11s
Tests alternative autoloader (PHP 7.4)	8s
Tests alternative autoloader (PHP 8.0)	8s
Tests alternative autoloader (PHP 8.1)	9s
Tests alternative autoloader (PHP 8.2)	10s
Tests alternative autoloader (PHP 8.3)	22s
PHPUnit coverage (PHP 7.4)	48s
PHPUnit lowest deps (PHP 7.3)	21s
Windows-Tests with PHP 7.1	1m 1s
Windows-Tests with PHP 7.2	57s
Windows-Tests with PHP 7.3	47s
Windows-Tests with PHP 7.4	47s
Windows-Tests with PHP 8.0	51s
Windows-Tests with PHP 8.1	45s
Windows-Tests with PHP 8.2	1m 2s
Windows-Tests with PHP 8.3	56s
	14m 11s

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