chore: Add permissions for CI with fork for testing #95

Job	Run time
CI / Context	1s
CI / Generate matrix	14s
CI / Check governance	1s
CI / 8.1 prf-low mysql57 phpunit silverstripe-composable-validators	2m 9s
CI / 8.2 mariadb phpunit silverstripe-composable-validators	2m 59s
CI / 8.3 mysql80 phpunit silverstripe-composable-validators	3m 0s
CI / 8.1 mysql57 phplinting	2m 9s
CI / 8.1 mysql57 js	4m 20s
CI / 8.1 mysql57 endtoend admin	29m 35s
CI / 8.2 mysql57 endtoend cms	17m 57s
CI / Dispatch tag release	0s
	1h 2m 25s

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