Add specific rubocop for tests

[VictorSNA]

We need to guarantee the code standard and quality in tests files!

For that mission we need to install, configure and fixes the offenses of rubocop-rspec:
https://github.com/rubocop/rubocop-rspec

Thanks!

DoD

• Rubocop-rspec installed and configured;
• No offenses being reported.

[toshitapandey]

@VictorSNA - May I pick this up?

[VictorSNA]

Hey, @toshitapandey for some reason we haven't received the message notification, please let us know if you are still interested and we apologize for the delay in response!

[toshitapandey]

@VictorSNA - yeah I'd like to pick this up.

[VictorSNA]

All right! Thanks @toshitapandey!

[rodrigoapereira]

Hey @toshitapandey we didn't have received the PR about this issue, let us know if you are still interested to work in this issue, maybe in Hacktoberfest of this year!

[toshitapandey]

@rodrigoapereira - Sure I will pick it up! Thank you!