Implement Series.str.ljust()/rjust()

[densmirn]

No description provided.

[AlexanderKalistratov]

I'm not sure if we really should create new file for each sample. Probably similar functionality into single file? Or create folder which unites all str methods?

[densmirn]

I'm not sure if we really should create new file for each sample. Probably similar functionality into single file? Or create folder which unites all str methods?

We should have separate documentation for each functionality. So I think we need to have separated examples, but I agree to put the examples in separate folders.