Ignore platform reqs on 8.4, add BC checker to CI #324

Job	Run time
ci / Generate job matrix	5s
ci / QA Checks (README Linting [8.1, locked], ubuntu-latest, laminas/laminas-continuous-integration-ac...	23s
ci / QA Checks (PHPUnit [8.1, locked], ubuntu-latest, laminas/laminas-continuous-integration-action@v1...	20s
ci / QA Checks (PHPUnit [8.1, lowest], ubuntu-latest, laminas/laminas-continuous-integration-action@v1...	21s
ci / QA Checks (PHPUnit [8.1, latest], ubuntu-latest, laminas/laminas-continuous-integration-action@v1...	20s
ci / QA Checks (PHPUnit [8.2, lowest], ubuntu-latest, laminas/laminas-continuous-integration-action@v1...	21s
ci / QA Checks (PHPUnit [8.2, latest], ubuntu-latest, laminas/laminas-continuous-integration-action@v1...	26s
ci / QA Checks (PHPUnit [8.3, lowest], ubuntu-latest, laminas/laminas-continuous-integration-action@v1...	23s
ci / QA Checks (PHPUnit [8.3, latest], ubuntu-latest, laminas/laminas-continuous-integration-action@v1...	20s
ci / QA Checks (PHPUnit [8.4, lowest], ubuntu-latest, laminas/laminas-continuous-integration-action@v1...	24s
ci / QA Checks (PHPUnit [8.4, latest], ubuntu-latest, laminas/laminas-continuous-integration-action@v1...	22s
ci / QA Checks (PHPCodeSniffer [8.1, locked], ubuntu-latest, laminas/laminas-continuous-integration-ac...	22s
ci / QA Checks (Psalm [8.1, locked], ubuntu-latest, laminas/laminas-continuous-integration-action@v1, ...	27s
	4m 34s

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