Add 10up-Default ruleset

[cadic]

Description of the Change

This PR adds support for 10up-Default ruleset.

Usage:

    steps:
      - uses: actions/checkout@v2
      - name: WPCS check
        uses: 10up/wpcs-action@stable
        with:
          use_local_config: true
          standard: '10up-Default'

Note: if local config include 10up-Default rule, we should specify the standard argument in the step configuration. It is required to correctly set up standards while performing the step.

Closes #9

How to test the Change

Tested on Simple Podcasting: https://github.com/10up/simple-podcasting/pull/196/files

Changelog Entry

Added - Support of 10up-Default ruleset

Checklist:

• I agree to follow this project's Code of Conduct.
• I have updated the documentation accordingly.
• I have added tests to cover my change.
• All new and existing tests pass.