Add documentation for string stripper.

[atompie]

Is your feature request related to a problem? Please describe.
String stripper is missing documentation

Describe the solution you'd like
Create a MD file with documentation. See other documentations eg. https://github.com/Tracardi/tracardi-api/blob/0.8.2-dev/docs/flow/actions/contains_pattern_action.md

Documentation should be added to tracardi/tracardi-api repo.

[Tejoooo]

@atompie can u assign me this

[ghost]

Hi @atompie , I'll take this up. Sorry I missed your comment on the original issue.

[atompie]

Hi @Tejoooo if you are looking for similar documentation task we have a lot of undocumented plugins that waits for anyone that would like to document them. Please see #830

[ghost]

@atompie , I have raised a PR in the tracardi-api repo.

[ghost]

The PR is merged. This can be closed. Thanks!