feat(sidecar): configurable ValidatorIndex

[namn-grg]

This PR adds CLI option to pass validator_index as comma-separated values i.e. --validator-index "1,2,3,4"

fixes #57

[merklefruit]

Looks good! Left a few nits. Just one note: have you been able to test the CLI option?
I don't think that --validator-index 1, 3, 4 would work because of the spaces after each comma, but I'm not sure.

Also, it would be nice to support specifying an array with the [2,5] notation specified in the issue. One way to do this could be to check if the flag value starts with [ in the parse_validator_indexes function, but maybe there are other ways too

[namn-grg]

Looks good! Left a few nits. Just one note: have you been able to test the CLI option? I don't think that --validator-index 1, 3, 4 would work because of the spaces after each comma, but I'm not sure.

Also, it would be nice to support specifying an array with the [2,5] notation specified in the issue. One way to do this could be to check if the flag value starts with [ in the parse_validator_indexes function, but maybe there are other ways too

@merklefruit as discussed since the brackets are an issue, I have changed it to be compatible with quotation marks i.e. --validator-index "1,2,3,4"

[merklefruit]

Great job with this one :)

[mempirate]

Looking good, small nit and updated some stuff as well

[thedevbirb]

Last nit, great job!