[actions] add permissions to GHA workflow #1846

Job	Run time
shellcheck_matrix (sh, nvm.sh)	59s
shellcheck_matrix (bash, bash_completion)	32s
shellcheck_matrix (bash, nvm-exec)	35s
shellcheck_matrix (bash, install.sh)	31s
shellcheck_matrix (bash, nvm.sh)	50s
shellcheck_matrix (dash, nvm.sh)	1m 4s
shellcheck_matrix (ksh, nvm.sh)	50s
shellcheck	3s
	5m 24s

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