[New] allow `.nvmrc` files to support comments #369

Job	Run time
shellcheck_matrix (bash, nvm.sh)	42s
shellcheck_matrix (sh, nvm.sh)	45s
shellcheck_matrix (dash, nvm.sh)	41s
shellcheck_matrix (ksh, nvm.sh)	43s
shellcheck_matrix (bash, install.sh)	26s
shellcheck_matrix (bash, bash_completion)	28s
shellcheck_matrix (bash, nvm-exec)	23s
shellcheck	9s
	4m 17s

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